Cyclic velox boiler

ABSTRACT

A cyclic velox boiler is described wherein solid carbonaceous fuels are burned in pressure vessel containers by cyclic compression and expansion with air or with air and steam as usual gas reactants. During compression air is forced deeply into the pores of the solid fuel and rapid primary burning to carbon monoxide results due to the large internal pore area available. During expansion the primary reacted gases emerge from the pores to mix and react fully with secondary air retained outside the pores in the container. Rapid and complete burning of the char fuel can be obtained in this two step, cyclic burning process and net useful mechanical work can be obtained from an expander engine. The containers and portions of the expander are cooled with water and the resulting steam can be used to generate additional work output via a steam power cycle.

CROSS REFERENCES TO RELATED APPLICATIONS

The invention described herein is an improvement upon my earlierdescribed invention entitled, "Improved Cyclic Char Gasifier," asdescribed in U.S. patent application Ser. No. 06/328,148, filing dateDec. 7, 1981.

The invention described herein is also related to my following U.S.patent applications:

(1) "Torque Leveller," Ser. No. 06/403,923, filing date July, 30, 1982.

(2) "Improved Cyclic Char Gasifier," Ser. No. 06/492,484, filing dateMay 6, 1983, a divisional application of Ser. No. 06/328,148.

(3) "Cyclic Solid Gas Reactor," Ser. No. 06/473,566, filing date Mar. 9,1983.

(4) "Further Improved Char and Oil Burning Engine," Ser. No. 06/367,019,filing date Apr. 9, 1982.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention is in the field of pressurized furnace steam boilers andalso the field of coal gasifier processes and apparatus utilizing cycliccompression and expansion to force reactant gases into the coal poresand to expand reacted gases out of the coal pores.

2. Description of the Prior Art

The common form of pressurized furnace steam boiler is the Velox boilerwherein an air compressor delivers compressed combustion air into asealed and pressurized furnace where combustion with added fuel occurs.The combustion gases are cooled when passing over the boiler heattransfer surfaces and steam is generated at pressure inside the boiler.After being thusly cooled, these combustion gases are then expandedthrough a gas turbine engine whose work output is used to drive thecombustion air compressor. By use of adequately high combustionpressures, the net work of the gas turbine engine can exceed the workinput to the air compressor and a net useful work output results. Ascompared to the more usual atmospheric pressure furnace steam boiler,the Velox boiler has the advantages of a smaller size for a givencapacity and the possibility of generating a net useful work output,whereas the atmospheric furnace boiler requires some work input to drivethe forced and induced draft fans. Descriptions of prior art Veloxboiler schemes are presented in references A and B.

The Velox boiler is a special form of combined cycle power plant. Themore common form of combined cycle power plant uses a gas turbine cyclewith a combustion air compressor, an uncooled combustion chamber, and agas turbine expander engine, and the expanded gases leaving the gasturbine expander engine are then passed through the atmospheric pressurefurnace of a steam boiler to generate steam at pressure for a steampower cycle. Because the gas turbine cycle combustion chamber isuncooled, considerable excess air must be used as a coolant to keep thecombustion gas temperatures below those producing damage ordeterioration of the gas turbine expander engine. The necessarycompression and expansion of this excess air for cooling reduces theefficiency of this common form of combined cycle steam power plant. Witha Velox boiler form of combined cycle power plant, the gas turbine cyclecombustion chamber is cooled by the steam boiler and excess cooling airis thus not needed and the resulting excess air efficiency losses areavoided in this way.

Combined cycle power plants of either the common type or the Veloxboiler type are today essentially limited to using liquid fuels orgaseous fuels and these fuels are today much more costly than coal. Whenpulverized coal is used in combined cycle power plants, serious bladeerosion occurs in the gas turbine expander engine due to the solid ashparticles produced.

Efforts to burn coal in lump form in combined cycle power plant gasturbine cycle combustion chambers, in order to avoid the blade erosionproblem, have encountered the following problems instead:

a. it is difficult to feed lump coal into combustion chambers, which arealways pressurized, by use of prior art lock hopper valves;

b. lump coal bed burning tends to produce channeling and thus tomaldistribute the air flow over the fuel lumps, a slight excess of airin one area burning the coal there more rapidly and thus causing yetmore air to flow through this consequently reduced flow resistancechannel, resulting in still more rapid coal burnup there;

c. fuel spreaders or a moving fuel bed grate are usually required toavoid excessive combustion air channelling and these are difficult tooperate and maintain inside a pressurized combustion chamber.

Some of the problems of lock hopper valves when operated at pressure aredescribed in reference C.

As a result of these dificulties with both pulverized coal firing andlump coal firing, few combined cycle power plants now use coal as fueldespite the greatly lower cost of coal. Nor are many new combined cyclepower plants likely to be built despite the appreciable improvement inplant efficiency of combined cycle plants since the only useable fuels,gas and oil, have become too costly.

Lump coal is commonly burned in moving beds in steam boilers whosefurnaces operate at essentially atmospheric pressure by use of movinggrates. Even at atmospheric pressure, however, moving grates are amaintenance problem due to the high temperatures at which they operateand the necessity for motion of the grate. Beds of lump coal are usuallycapable of removing a higher proportion of the sulfur dioxide from fuelsulfur burnup than are pulverized coal burners due to the closer contactof the sulfur dioxide gas with either basic ash ingredients from thecoal or with added basic materials such as dolomite.

It would thus be of great benefit to have available for use in combinedcycle power plants a combustion scheme for use in pressurized combustionchambers which could burn lump coal in a fixed bed without the need forfuel spreaders or moving grates and whose lock hopper valves could beoperated at low pressures.

The term water is used herein and in the claims to mean either liquidwater or steam, which is defined as water vapor, or a mixture of liquidwater and steam.

The term boiler means is used herein and in the claims to mean anenclosed pressure vessel with liquid water inlet and steam outlet andwith heating surfaces for boiling the enclosed liquid water flowing intothe liquid water inlet and for heating the resulting steam at pressureabove atmospheric and comprising the usual steam boiler auxiliaries suchas pressure relief valves, water level indicators if useable, exteriorinsulation, etc. Those heating surfaces of a boiler means which directlyview a combustion chamber or solid fuel bed are herein and in the claimsreferred to as radiant heaters since significant heat transfer can occurto these surfaces by radiation from the burning fuel as well as byconvection from combustion gases. Those heating surfaces of a boilermeans which do not directly view a combustion chamber or solid fuel bed,or whose view thereof shows only small area, are herein and in theclaims referred to as convection heaters since most of the heat transferto these surfaces occurs by convection from hot combustion gases. Aboiler means may comprise but a single heating surface, either a radiantheater or a convection heater, but usually more than one heater is usedand both radiant heaters and convection heaters are frequently used incombination in a single boiler means. A boiler means can be of theonce-through type with liquid water entering the boiler liquid waterinlet and the water flows unidirectionally through the boiler heatingsurfaces toward the boiler steam outlet where the water emerges assteam. Alternatively, a boiler means can be of the separator andrecirculator type wherein liquid water and steam pass into a steam andliquid water separator, such as a steam drum, after passing through aprincipal portion of the boiler heating surfaces. The liquid waterseparated by the separator is then recirculated back through the sameprincipal portion of the boiler heating surfaces, either by a forcedrecirculator pump or by a natural convection recirculator. The steamfrom the separator continues on to superheater surfaces for furtherheating or to the boiler steam outlet.

Since boilers usually operate at pressures well above atmospheric, afeedwater pump and feedwater pump drive means are used to pump liquidwater into the boiler liquid water inlet at a feedwater flow rate equalto the rate at which steam is being formed within the boiler and isleaving via the boiler steam outlet. Various types of feedwater pumpflow rate controls are used to insure an adequate flow of liquid waterinto the boiler to prevent overheating of any of the heating surfaces ofthe boiler means.

The term superheater means is used herein and in the claims to mean anenclosed pressure vessel with steam inlet and superheated steam outletand with heating surfaces for superheating the enclosed steam flowinginto the steam inlet at pressures above atmospheric. Superheaters can beof the radiant heater type or of the convection heater type or of bothtypes together in combination.

The term reheater means is used herein and in the claims to mean anenclosed pressure vessel with steam inlet and reheated steam outlet andwith heating surfaces for reheating the enclosed steam flowing into thesteam inlet at pressures above atmospheric. Reheaters can be of theradiant heater type or of the convection heater type or of both typestogether in combination.

Superheaters and reheaters are very commonly used in fossil fuel firedsteam electric power plants in order to keep the steam free of liquidwater as it expands through the steam turbine so that blade erosion byliquid drops can be avoided.

The steam side of a boiler means, a superheater means or a reheatermeans is that side of the pressure vessel in contact with water. The gasside of a boiler means, a superheater means or a reheater means is thatside of the pressure vessel in contact with combustion gases or viewingthe combustion chamber or fuel bed or both.

The term oxygen gas is used herein and in the claims to mean oxygenmolecules not combined with any other chemical elements. Air, forexample, is a gas containing appreciable quantities of oxygen gas.Carbon dioxide, on the other hand, is a gas devoid of oxygen gas eventhrough oxygen atoms exist therein combined with the carbon atoms.

The term char fuel is used herein and in the claims to include anycarbon containing fuel which is either a solid or can be transformed atleast partially into a carbonaceous solid when volatile portions thereofare removed. Included as char fuels within this definition are coal,coke, wood, wood charcoal, oil shale, petroleum coke, garbage, woodbark, wood wastes, agricultural wastes and other carbonaceous materialsas well as mixtures of these fuels.

References

A. "Steam Power Stations," G. A. Gaffert, McGraw Hill, New York, 1940,2nd edition, page 228 to 229 and FIG. 172.

B. "Applied Energy Conversion," B. G. A. Skrotzki and W. A. Vopat,McGraw Hill, New York, 1945, 1st edition, 6th impression, page 314 to315 and FIG. 9-2.

C. "The METC Prototype Lockhopper Valve Testing and Development ProgramReview," W. J. Ayers Jr., U.S. Department of Energy, ASME Paper No.83AESI, 1983.

D. "Steam--Its Generation and Use," Babcock and Wilcox Co., New York,38th edition, 1972.

E. "Combustion Engineering," G. R. Fryling, editor, CombustionEngineering Inc., New York, 1966, revised edition.

F. British Pat. No. 492,831 of Sept. 28, 1983

G. U.S. Pat. No. 2,714,670 of Aug. 2, 1955

H. U.S. Pat. No. 4,047,901 of Sept. 13, 1977

I. U.S. Pat. No. 1,913,395 of June 13, 1933

J. U.S. Pat. No. 1,992,323 of Feb. 26, 1935

K. U.S. Pat. No. 3,734,184 of May 22, 1973

L. U.S. Pat. No. 2,225,311 of Dec. 17, 1940

M. U.S. Pat. No. 2,624,172 of Jan. 6, 1953

N. U.S. Pat. No. 4,085,578 of Apr. 25, 1978

O. U.S. Pat. No. 2,675,672 of Apr. 20, 1954

SUMMARY OF THE INVENTION

A cyclic Velox boiler plant of this invention comprises a cyclic chargasifier plant, of the oxidation type using pressure vessel containersand preferably modified to carry out essentially full burning of thefuel to carbon dioxide and water at pressure within the containers ofthe cyclic char gasifier plant, to which is added a steam boiler which,being heated by the cyclic char gasifier combustion gases, acts to cooldown these combustion gases before they enter the expanders of thecyclic char gasifier plant. The steam thusly generated can be used in asteam power cycle with a steam turbine to generate work outputadditional to any generated by the expander engine of the cyclic chargasifier plant. In this way a combined cycle power plant of the cyclicVelox boiler type is created wherein char fuels can be burned in lumpform in a fixed fuel bed and hence without problems of expander engineblade erosion due to ash carried over from the combustion chambers, andthis is one of the beneficial objects of this invention.

The several containers of the cyclic char gasifier plant are preferablyenlarged sufficiently to carry out full burning and become combustionchambers each of which cycles between a high pressure and a lowpressure. Hence, refueling and ash removal can be carried out atintervals at low pressures and this is another of the beneficial objectsof this invention.

BRIEF DESCRIPTION OF THE DRAWINGS

A schematic diagram of one form of cyclic Velox boiler plant is shown inFIG. 1.

The changeable gas flow connections, between a single example container,and each stage, of the compressor and each stage, of the expander of acyclic Velox boiler plant are shown schematically in FIG. 2.

A cross-section view of a single pressure vessel container is shown inFIG. 3.

A transverse cross section, A--A, of FIG. 3 is shown in FIG. 4.

A schematic diagram of a cyclic Velox boiler plant is shown in FIG. 5.

Flow distributors are shown in FIG. 6 for distributing water flowbetween the several tubes of a radiant heater.

A combustion steam flow control means is shown schematically in FIG. 7for use as a steam superheat controller.

A drive means suitable for use with a refuel means or a coke removalmeans is shown in FIG. 8, and a portion of a refuel control meanstherefor is shown in FIG. 9, and a portion of a coke removal controlmeans therefor is shown in FIG. 12.

A portion of a control scheme for pressure control of refuel and cokeremoval and of the changeable gas flow connections is shownschematically in FIGS. 10 and 11.

Another form of cyclic Velox boiler plant with fixed series connectedradiant heaters is shown schematically in FIG. 13.

An adjustable water flow distributor and control means is shown in FIG.14.

A means for controlling the outflow of gases from a container duringexpansion is shown in FIG. 15.

An alternative pneumatic control means for controlling the changeablegas flow connections and the refuel and coke removal connecting is shownpartially in FIGS. 16 and 17.

A means for controlling gas flow rate through the expander is shownpartially in FIG. 18.

DESCRIPTION OF THE PREFERRED EMBODIMENTS A. Basic elements

All forms of the cyclic Velox boilers of this invention comprise thefollowing elements;

1. A cyclic oxidation char gasifier plant of the pressure vesselcontainer type as described in my co-pending, cross-referenced, U.S.patent application Ser. No. 06/328,148, filing date Dec. 7, 1981. Thiscyclic char gasifier portion of this invention comprises combinations ofreactant gas compressors with drive means, two or more pressure vesselchar fuel containers with means for refueling, reacted gas expanders,together with means for connecting each container in turn, first to eachstage of the compressor in order of increasing pressure, and then toeach stage of the expander in order of decreasing pressure. With thisapparatus the char fuel within the containers is first compressed withfresh reactant gases containing oxygen gas and the resulting primaryreacted gases are then expanded out of the char fuel pores and thiscycle is repeated with fresh reactant gas for each compression and withreacted gases removed during each expansion. Preferably the containersare only partially filled with char fuel so that extra reactant oxygengas is available in the resulting dead volume to react with the primaryreacted gases, emerging from the pores during expansion, to formsecondary reacted gases. In this way complete burning of the char fuelto carbon dioxide can be achieved within the containers. Preferably theexpander is an expander engine capable of producing work and foroxidation gasifiers this expander work can exceed the work ofcompression and a net work output results which is one of the beneficialobjects of this invention. When such work expanders are used a workabsorbing element is also used such as an electric generator. Thecontainers for the char fuel are sealed pressure vessels fitted with arefuel means to replace the char fuel as it is reacted to gases.Usually, a coke removal means to remove ashes is also fitted to thepressure vessel containers. A wide range of char fuels can be gasifiedand burned in the cyclic char gasifier portion of this inventionincluding coal, wood, oil shale, and other carbonaceous materials andthese char fuels can be used alone or in combination.

The term reactant gas is used herein to refer to those gases beingcompressed into the pores of a char fuel. The resulting gaseous productsof reaction of the reactant gas and the char fuel within the char poresare referred to herein as the primary reacted gases. When primaryreacted gas is removed from the pores during expansion, it may reactfurther with reactant gases retained outside the pores and the gaseousproducts of this secondary reaction outside the pores are hereinreferred to as secondary reacted gases.

Where air or air and combustion steam are used as reactant gases, theprimary reacted gases contain carbon monoxide and may contain hydrogenas shown by the following reaction balance for complete reaction tocarbon monoxide:

    (2+a)C+O.sub.2 +aH.sub.2 O+3.76N.sub.2 →(2+a)CO+aH.sub.2 +3.76N.sub.2

Wherein (a) is the molal ratio of combustion steam to oxygen. Wheresufficient reactant air is retained outside the char pores to fully burnthe emerging primary reacted gases during expansion, the secondaryreacted gases contain carbon dioxide and may contain water vapor asshown by the following reaction balance for complete reaction to carbondioxide:

    [(2+a)CO+aH.sub.2 +3.76N.sub.2 ]+ (1+a)O.sub.2 +(1+a)3.76N.sub.2 →(2+a)CO.sub.2 +aH.sub.2 O+7.52N.sub.2 +3.76aN.sub.2

In most cases, some excess air will be needed to carry out thesesecondary reactions to essential completion.

To get these oxidation gasification reactions started, the char must bebrought up to its rapid burning temperature. This rapid burningtemperature differs somewhat between different chars but almost all charfuels will react rapidly with air at temperatures of about 1000° F. orgreater and some char fuels react readily at temperatures as low as 800°F. For startup the char fuel can be heated up to its rapid burningtemperature by several different means of which the following areexamples:

(i) Cyclic compression and expansion with preheated air or preheatedoxygen-rich gas is a preferred starting means. This air preheating canbe done in several ways as for example with electrical heaters orcombustion-fired heaters and preferably after the air has beencompressed.

(ii) Cyclic compression and expansion with air on a char fuel soakedwith a volatile hydrocarbon which latter can be spark or compressionignited and thus heat up the compressed air and char fuel.

(iii) Where very high pressure ratios are used, the cyclic compressionand expansion may alone be sufficient to bring the char fuel up to itsrapid burning temperature.

(iv) Electrical or furnace heating schemes can also be utilized.

Combinations of these and other starting means can also be used.

Once started, the reaction of the char fuel with oxygen will elevate thechar temperature further and burning can thereafter continue without useof the startup means, provided the average reacted gas temperatures arekept sufficiently high. When fresh char fuel is introduced, it will besoon heated up to the rapid reaction temperature by adjacent hot andburning char. As reactant gases enter the char pores during compression,both oxygen and steam react rapidly with adjacent hot carbon and thechar fuel and primary reacted gases tend to reach the same averagetemperature. Hence, we prefer to keep the average primary reacted gastemperature above the rapid reaction temperature of the char fuel (circa1000° F., 1460° Rankine). As combustion steam oxygen ratio, a, isincreased, the average temperature of the primary reacted gasesdecreases since the steam oxidation of carbon is endothermic. If toomuch steam is used, the average reacted gas temperature, and with it theaverage char temperature, will drop below the char rapid reactiontemperature and the oxidation gasification reaction will die out. Hence,the maximum value of the overall steam oxygen ratio for practical use isset at about that value, yielding an average primary reacted gastemperature equal to the char fuel rapid burning temperature. Forexample, an approximate calculation for a cycle pressure ratio ofcompression of 34 to 1, using unpreheated air with steam as reactantgases, showed that the overall combustion steam oxygen ratio, a, shouldnot exceed about 1.50 if reacted gas average temperatures are to be keptabove about 1000° F. Higher values of steam oxygen ratio can be used athigher values of cycle pressure ratio and with preheated reactant gases.

Any of the several different kinds of compressors, such as pistoncompressors, roots blowers, centrifugal compressors, axial flowcompressors, etc., can be used alone or in combination as the reactantgas compressor. Multistage compressors may be preferred in cases where ahigh cycle pressure compression ratio is used in order to obtain highwork output. The particular definition of a stage of a compressor or anexpander is used herein and in the claims to be a portion of saidcompressor or expander which has a gas flow inlet and a gas flow outlet,both of which make connections external from the compressor or expander.For example, a single stage thusly defined could contain several pistonand cylinder units acting to compress gas in series provided that allgas flow between such units went exclusively between units and notexternally. When two or more compressor stages are connected in serieswith the delivery of a first stage connected to the supply of a secondstage, whose delivery may in turn be connected to the supply of a thirdstage, the pressure at delivery necessarily rises from first stage tosecond stage to third stage and so on since each succeeding compressorstage receives at supply gas already raised to a higher pressure by thepreceding stage. Hence, such later compressor stages connected in seriesare commonly and herein referred to as higher pressure stages.

Any suitable drive means can be used to drive the compressor such aselectric motors, steam turbines, or preferably the expander engine ofthe char gasifier plant itself. Either constant speed drive or variablespeed drive of the compressor can be used.

Any of the several different kinds of expander engines, such as pistonengines, radial flow turbines, axial flow turbines, etc. can be usedalone or in combination as the reacted gas expander engine. A simpleblowdown pipe can alternatively be used as a low-cost, non-engineexpander but the available work of expansion is then lost so this typeof expander is probably practical only when other work sources fordriving the compressor are readily available and cheap. Multistageexpanders may be preferred where a high cycle compression ratio is usedto obtain high work output and so that high expander efficiency can beobtained by operating each stage over only that narrow range ofpressures for which it was optimally designed. When two or more expanderstages are connected in series, with the discharge of a first stageconnected to the inlet of a second stage whose discharge may in turn beconnected to the inlet of a third stage, the pressure at inletnecessarily decreases from first stage to second stage to third stageand so on since each succeeding expander stage receives at inlet gasalready expanded to a lower pressure by the preceding stage. Hence, suchlater expander stages connected in series are commonly and hereinreferred to as lower pressure expander stages. Expander stages or groupsof stages not thusly connected together in series are herein referred toas separate expanders. The work output of the expander engine can beabsorbed in one or a combination of ways, as, for driving the reactantgas compressor, for driving an oxygen enrichment plant, or for drivingan electric generator. The flow rate of reacted gases to the expander isset by the rate at which reactant gases are delivered into the char fuelpores by the compressor, and by the kind of gasification reactionstaking place with the char fuel and subsequently with reactant gasoutside the pores. The expander must pass this reacted gas flow rate sothat the reacted gases are fully expanded out of the char pore spacedown to the minimum cycle pressure in time to make way for the freshreactant gases of the next following cycle of compression. This desiredcontrol of expander flow rate of reacted gases can be accomplished inone or a combination of several ways as, for example, by throttling thereacted gas pressure, by controlling nozzle flow area for blowdownexpanders and for turbine expanders, by controlling cut-off timing forpiston expanders. Throttling control, while mechanically simple, reducesthe work output available from an expander engine. Various means ofcontrolling nozzle flow area are already well known in the art of steamand gas turbine. Various means of controlling the timing of cut-off offlow of high pressure gas into the cylinder of a piston expander engineare already well known in the art of piston steam engines. One schemefor assuring that the desired minimum cycle pressures will be achievedwithin the cycle time interval is to actuate the reacted gas flow ratecontroller of the expander in response to the minimum cycle pressureactually reached within the containing means, expander flow rate beingincreased when minimum cycle pressure increases and being decreased whenminimum cycle pressure decreases. This same scheme of control can alsobe applied to the particular case where multistage expansion is used,and each stage is connected to a separate containing means, and eachcontaining means is connected in turn to each expander stage asexpansion proceeds as will be further described hereinbelow. For thisparticular case, the reacted gas flow rate controller of each expanderstage can be actuated as described above by the minimum pressure reachedwithin the connected containing means just prior to when that containingmeans is to be next connected to the next following expander stage.Alternatively, the reacted gas flow rate controller can be actuated asdescribed by the starting pressure of each containing means as it firstconnects to that expander stage being controlled. The expander must bedesigned to possess a maximum reacted gas flow capacity at least equalto the maximum flow rate available from the containing means and chargasification process being used when operating with the desired minimumcycle pressure.

Where the reactant gas compressor is separately driven as by an electricmotor, the expander engine will start up and run as soon as highpressure reacted gas is admitted into the expander. Where the reactantgas compressor is driven only by an expander engine, startup can beaccomplished in various ways as, for example, by spinning up theconnected compressor and expander by an electric motor, or by admittinghigh pressure steam to the expander engine inlet.

The total number of separate containers for a plant must at least equalthe sum of the number of compressor stages plus the number of expanderstages in order that each such stage always has a connection into acontainer. The connectings which the containers make to compressordischarges and to expander inlets change and such connectings are hereinand in the claims referred to as changeable gas flow connectings. Othergas flow connectings, as between stages of a compressor or an expander,are fixed and remain open whenever the plant is operating, and these areherein and in the claims referred to as fixed open gas flow connections.Changeable gas flow connections can be opened and closed while the plantis operating.

Although the opening and closing of the changeable gas flow connectionscan be carried out entirely by hand, it will usually be preferable toaccomplish this control automatically.

A simple control scheme is to set a particular value of cycle time, tc,and time between changes of connectings, tcc, and then observe theactual maximum cycle pressures, PM, achieved, and then increase tc whenPM is too low or decrease tc when PM is too high. This adjustment of tcin response to PM can be done by hand or automatically by methodsalready known in the art of controls. Other cycle time control methodscan also be used as, for example, setting a particular value of PM andwhen this pressure is reached by each container in turn, a pressuresensor triggers the several valves to change connectings and start thenext time interval in the sequence. Whatever cycle time control schemeis used, it functions by actuating the several valves and connections ofthe changeable gas flow connectings so that each container in turn isconnected in sequence separately to each compressor stage in order ofincreasing pressure and then separately to each expander stage in orderof decreasing pressure, and so that each compressor stage and eachexpander stage is always connected to a single container.

The term cyclic oxidation char gasifier plant is used herein and in theclaims to mean the combination of elements as described hereinabove andas described in my co-pending, cross-referenced U.S. patent application,Ser. No. 06/328,148, filing date Dec. 7, 1981.

2. A boiler means for heating and boiling liquid water at pressure andfor superheating the resulting steam, if desired, at least one portionof which is a radiant heater located on the interior surface of one ofthe pressure vessel containers of the cyclic oxidation char gasifier.Preferably, a radiant boiler heater is located in each of the pressurevessel containers. This boiler performs the dual functions of generatingsteam for external use, as in a steam power plant cycle, and also ofcooling down the combustion gases formed inside the containerssufficiently for safe use in the expander of the cyclic gasifier plant.

3. A feedwater pump and drive means connected to the boiler means so asto pump liquid water into the boiler water inlet against the boilersteam pressure with a control means for controlling the water flow rate.Usually, the control means functions to keep the liquid water quantityinside the boiler adequate to prevent overheating of any boilersurfaces.

4. A sensor and control means for sensing the char fuel quantity withineach container and operative upon the refueling means of the cyclic chargasifier plant to keep the char fuel quantity within selected maximumand minimum limits in each container. The cyclic char gasifier plant canbe operated as a gasifier to make a fuel gas, if desired, and in thiscase each container is to be kept essentially full of char fuel so therefuel control schemes of the cyclic char gasifier can be used. In mostapplications, however, the char fuel is to be burned essentiallycompletely to carbon dioxide and water. For this latter preferred case,sufficient compressed air is to be kept outside the char fuel pores atthe end of compression so as to burn the emerging pore reacted gasesfully during subsequent expansion. Hence, in this complete burning case,the char fuel is controlled so as to occupy only a portion of theinterior volume of the pressure vessel containers. Various kinds of charfuel volume sensors can be used such as, photoelectric sensors of theheight of the char fuel and ash pile inside the container, or sensors ofthe carbon monoxide and oxygen content of the combustion gases leavingthe container to enter the expander inlets.

Although in principle any cyclic oxidation char gasifier plant of thepressure vessel container type can be adapted for use in the cyclicVelox boiler combination of this invention, it will usually bepreferable to use cyclic oxidation char gasifier plants which do nothave inert gas compression for the final compression step since completeburning of the char fuel is usually to be carried out. In someapplications it may also be preferable to use the simpler singleexpander rather than separate expanders.

Other elements may be added to these basic elements and modifiedelements may be used for certain applications.

B. Added and modified elements

In addition to the radiant heaters inside the containers, convectionheater means can be added to the expander stage inlets not only togenerate additional steam and for superheating or reheating of steam,but also to additionally cool the combustion gases before they enter theexpander. These convection heaters can be of various types as is alreadywell known in the art of steam boiler design as described in chapter 12of reference D, for example. Preferably, the gas side of each of theseconvection heaters is positioned between the expander stage inlet andthe changeable gas flow connections thereto so that all of thecombustion gases which flow from the connected containers into the inletof that stage of the expander flow first through the gas side of theconnected convection heater and are further cooled thereby. Theseexpander inlet convection heaters can be thusly used on one or more ofthe expander stage inlets. If used to generate additional steam or tosuperheat steam already generated in the radiant heaters inside thecontainers, the steam side of these expander inlet convection heaters isso connected to the radiant heaters that at least some of the waterwhich flows through radiant heaters flows subsequently through theseexpander inlet convection heaters. If used as a reheater, an expanderinlet convection heater steam side is connected to receive steam fromthe source of steam to be reheated and to deliver steam into a reheatedsteam pipe. One or more of these convection heaters can be placed oneach of one or more of the expander inlets.

In theory, the combustion gases which flow from connected containersinto the inlets of the expander stages can be cooled by use of theseexpander inlet convection heaters down almost to the temperatures of thewater in the steam side of these heaters. In practice, however, we willrarely wish to cool these combustion gases much below that temperatureat which adequate expander durability is obtained. Further cooling ofcombustion gases at expander inlet below this adequate durabilitytemperature unnecessarily reduces the work output of the expanderengine. In usual practice, therefore, these expander inlet convectionheaters are a principal design variable with which to achieve desiredexpander inlet temperatures for adequate durability.

The changeable gas flow connections between containers and expanderinlets are preferably fitted with cooling jackets through which watercan be circulated to cool these pipes and valves.

Further additionally to the radiant heaters inside the containers one ormore exhaust gas convection heaters can be added to the expanderdischarge so that all of the combustion gases leaving an expander passnext through the gas sides of these exhaust gas heaters. These exhaustgas convection heaters can be used in various ways such as: for afeedwater heater to heat up water before it enters the radiant heatersinside the containers; for further heating and boiling of waterrecirculating to radiant heaters inside the containers; for superheatingthe steam leaving the boiler means or leaving the convection heaters onthe expander stage inlets. For feedwater heating the steam side of anexhaust gas heater is so connected that all of the feedwater which flowsinto the radiant heaters flows previously through the exhaust gasfeedwater heater. For superheating of steam the steam side of an exhaustgas heater is so connected that all of the steam which flows out of theboiler means flows subsequently through the exhaust gas superheater.When more than one heater is used on a single expander, the gas side ofthese separate exhaust gas heaters will usually be connected to theexpander discharge so that the expander exhaust gas passes first throughthe superheater and last through the feedwater heater.

The steam capacity and boiler efficiency of a cyclic Velox boiler plantcan be greatly increased by use of these exhaust gas heaters since,apart from cost and pressure drop considerations, energy can inprinciple be extracted from the combustion gases in these exhaust gasheaters up to the point where the combustion gases approach thefeedwater entry temperature. In usual practice, therefore, these exhaustgas heaters are a principal design variable with which to achievedesired boiler efficiency.

Where separate expanders are used, it will frequently be preferable touse separate exhaust gas heaters on one or all of the separate expanderdischarges since the exhaust gas temperatures may differ between theseparate expanders. With equal proportions of heat transferred from allcombustion gas portions up to the expander inlet the highest temperatureexhaust gas will discharge from that expander last to connect to eachcontainer and the lowest temperature exhaust gas will discharge fromthat expander first to connect to each container. These temperaturedifferences can be used to advantage as, for example, by placing a steamsuperheater exhaust gas heater on the discharge of that expander last toconnect to each container and by placing a feedwater heater exhaust gasheater on the discharge of that expander first to connect to eachcontainer.

Where several radiant heaters inside containers are used, these may beconnected together on the steam side in series, or in parallel, or inseries-parallel combination. For fixed series connection, whatever waterflows through one radiant heater flows also through all radiant heaters.For parallel connection, whatever water flows through one radiant heaterdoes not flow through any other parallel radiant heater during any onerecirculation, and it is necessary that at least sufficient water flowthrough each radiant heater to prevent overheating of the heatermaterials.

For efficient utilization of the heat transfer surfaces of seriesconnection radiant heaters, we prefer that the coldest entering waterenter the series at that active radiant heater whose container isconnected to the first compressor stage outlet and that the water flowdirection thereafter be in series through active radiant heaters whosecontainers connect to compressor stages in the direction of increasingcompressor stage delivery pressure. Thereafter, the water flow directionis preferably in series through active radiant heaters whose containersconnect to expander stages in the direction of increasing expander stageinlet pressure. By active radiant heaters is meant such heaters insidethose containers currently connected to compressor outlets and expanderinlets. This preferred series connection of radiant heaters placesincreasingly higher temperature water in heat exchange contact withincreasingly higher temperature gases. But to achieve this preferredresult, the steam side connections of each radiant heater must bechanged at the same time that the changeable gas flow connectionsbetween the several containers and the compressor and expander arechanged. Hence, for this preferred series connection pattern changeablewater flow connections are needed on the water inlet and steam outlet ofeach radiant heater together with a means for opening and closing thesechangeable water flow connections. Additionally, the means forcontrolling the means for opening and closing the changeable gas flowconnections of the cyclic char gasifier can be expanded to also controlthe opening and closing of these changeable water flow connections sothat water flows through the series connected radiant heaters in thepreferred direction discribed above. These changeable water flowconnecting means, the means for opening and closing them, and the meansfor controlling the means for opening and closing, can be similar to thechangeable gas flow connecting means, the means for opening and closing,and the means for controlling the means for opening and closing, asdescribed in my earlier application Ser. No. 06/328,148, and alsodescribed hereinafter.

For efficient cooling of the heat transfer surfaces of parallelconnected radiant heaters and for efficient cooling of the combustiongases flowing toward the expander inlets, we may sometimes prefer todistribute the water flow among the several radiant heaters so that thewater leaving each radiant heater has approximately the same enthalpy asthat leaving all other radiant heaters. Radiant heaters insidecontainers connected to compressor stage outlets will experience mostlyradiation heat transfer from the contained char fuel since dead gasspaces are filled with relatively cold compressed air. Radiant heatersinside containers connected to expander stage inlets will experience notonly radiation heat transfer from the contained char fuel but alsoconvection and radiation heat transfer from the complete combustiongases formed during expansion when reacted gases emerge from the charfuel pores and burn fully with the air retained outside the pores.Hence, the heat transfer rate is higher to those radiant heaters insidecontainers connected to expander stage inlets than to those radiantheaters inside containers connected to compressor stage outlets. Butsince any one container and its radiant heater is connected in turn toall compressor stage outlets and then to all expander stage inlets, weneed to change the distribution of water flow among the several parallelradiant heaters whenever the changeable gas flow connections tocontainers are changed, with relatively more water being distributed tothose radiant heaters whose containers are connected to expander stageinlets than is distributed to those radiant heaters whose containers areconnected to compressor stage outlets. For this purpose, a steamenthalpy sensor in each radiant heater steam outlet can operate via acontrol means upon the water flow distributor means to increase waterflow to that radiant heater when enthalpy rises above a set value and todecrease water flow to that radiant heater when enthalpy drops below aset value. Various types of steam enthalpy sensors can be used such astemperature sensors when the steam at exit is to be superheated orheater wall temperature sensors when the steam at exit is to be wet orsaturated. This enthalpy sensor control of water flow distributionbetween parallel radiant heaters may be preferred for once-through typeboilers such as are used for steam pressures near or above the criticalpressure.

Where steam pressures are sufficiently below the critical pressure, asteam separator, such as a steam drum, can be used after the radiantheaters and the separated liquid water recirculated back through theradiant heaters again. For this case with parallel radiant heaters, wemay prefer to recirculate a large volume of liquid water distributedessentially equally between the separate radiant heaters so that thesteam is always very wet in all radiant burners. This recirculationscheme avoids constant adjustment of the flow distribution between theradiant heaters and a steam enthalpy sensor and flow distributioncontrol means is not needed.

Removal of the ash, produced by the burning of the char fuel, from eachcontainer can be accomplished intermittently by a coke removal transfermeans and connecting means, such as are described in my earlierapplication Ser. No. 06/328,148. Additionally, a sensor and controlmeans for sensing the quantity of ashes within each container is usedand acts upon the connecting means, to connect the coke removal transfermeans whenever the ash quantity within any container exceeds a maximumset value, and to disconnect the coke removal transfer means wheneverthe ash quantity within any container becomes less than a minimum setvalue. Temperature sensors of ash quantity can be used such as aredescribed in the application Ser. No. 06/328,148. Other ash quantitysensor means can alternatively be used such as, with char and ash pileheight control, a sensor of the carbon monoxide and oxygen content ofthe combustion gases leaving the container to enter the expander inlets.

Where the ash is maintained in a molten state, it can be removedcontinuously via a bottom orifice in each container and this orificethen becomes a coke removal transfer means which is always connected. Toseal the container against gas leakage, the molten ash level is keptsufficient to cover the orifice, as by addition of extra ash materialsto the char fuel or by adjustment of the ash orifice area. One exampleof such a continuous molten ash removal orifice is shown in FIG. 15wherein the molten ash volume, 2371, flows continuously through theorifice, 2381, which is sealed against gas leakage by maintaining themolten ash volume, 2371, always adequate to cover the orifice, 2381.

C. Description of plant operation

One particular example of a cyclic Velox boiler plant is shownschematically in FIG. 1 and comprises the following:

a. The reactant gas compressor, 1, has three compressor stages, 2, 3, 4,whose outlets, 5, 6, 7, are currently connected via changeable gas flowconnections 8, 9, 10, to three containers 11, 12, 13, undergoingcompression with air as reactant gas entering the first stage compressorinlet, 14, from the air precompressor, 15, driven by the electric motor,16.

b. The reacted gas expander, 17, has three expander stages, 18, 19, 20,whose inlets, 21, 22, 23, are currently connected via changeable gasflow connections, 26, 25, 24, to three containers, 27, 28, 29,undergoing expansion of the combustion gases formed inside thecontainers by reaction of the char fuel therein with the air compressedtherein, with the exhaust gas leaving the last stage of the expander viathe discharge, 30.

c. Combustion steam from a source, 31, is admitted at pressure via thedelivery means, 32, 33, to those containers, such as 12 and 13, whichare being compressed by the two higher pressure stages, 3, 4, of thecompressor, 1.

d. For the particular example cyclic Velox boiler plant of FIG. 1, airis being used as the source of gas containing appreciable oxygen gas,but oxygen enriched air or other types of sources could also be used.

e. An additional container, 34, is used in this example so that thetotal number of containers exceeds the number of active containers equalto the sum of the number of compressor stages and the number of expanderstages. In this way as each container finishes expanding into the lowestpressure expander stage, 18, it is disconnected for a time period fromboth the expander and the compressor and at low pressure can undergorefueling with fresh char via the connected refuel transfer means, 35,and can also undergo coke removal via the connected coke removaltransfer means, 36, before connecting again to the lowest pressurecompressor stage, 2, to commence compression again.

f. Each of the pressure vessel containers, 11, 12, 13, 27, 28, 29, 34,contain a volume of porous char fuel which as it burns up is replaced bythe refuel means.

g. A power means, 42, supplies any extra power needed to drive thecompressor, 1, and also absorbs any extra power output of the expander,17.

h. Each of the containers, 11, 12, 13, 27, 28, 29, 34, has changeablegas flow connections to each of the compressor stage outlets 5, 6, 7,and to each of the expander stage inlets, 21, 22, 23; in FIG. 2 areshown these several changeable gas flow connections, 8, 37, 38, tocompressor stage outlets, 5, 6, 7, respectively and, 39, 40, 41, toexpander stage inlets, 21, 22, 23, respectively, for the singlecontainer, 11, and all containers are similarly fitted.

i. All of these changeable gas flow connections, such as, 8, 9, 10, 24,25, 26, 37, 38, 39, 40, 41, etc. are opened and closed by means foropening and closing, such as a solenoid and spring actuator; a controlmeans operates upon the means for opening and closing so that; eachcontainer is opened for a time period separately to each outlet, 5, 6,7, of each stage, 2, 3, 4, of the compressor, 1, in a subsequence oftime periods of open gas flow connections to compressor outlets, thiscompressor subsequence proceeding in time order of increasing compressorstage delivery pressure and hence in the time order, 2, 3, 4; eachcontainer is opened for a time period separately to each inlet, 21, 22,23, of each stage, 18, 19, 20, of the expander, 17, in a subsequence oftime periods of open gas flow connections to expander inlets, thisexpander subsequence proceeding in time order of decreasing expanderstage inlet pressure and hence in the time order, 20, 19, 18; thesubsequence of connections to compressor outlets is followed by thesubsequence of connections to expander inlets and these togethercomprise one sequence of time periods of open gas flow connections, eachsuch sequence for each container being followed by a time period forrefueling and for coke removal and the sequence of time periods is thenrepeated; each compressor outlet, 5, 6, 7, always has an open gas flowconnection to a single container and each expander inlet, 21, 22, 23,always has an open gas flow connection to a single container wheneverthe plant is operating.

j. The example char gasifier plant of FIG. 1 has a common shaft, 237,for all stages of the compressor, 1, and expander engine, 17, and thisshaft connects in turn to the power means, 42, such as an electricmotor-generator. However, separate shafts and separate work input and/orwork output devices can be used for some or all stages of the multistagecompressor and the multistage expander engine and such separate shaftarrangements may be preferred where both piston and turbine stages areused together in the compressor and/or the expander engine. Additionalconnections shown in the example of FIG. 1 are: the air supply pipe, 14,to the intake of the low pressure compressor stage, 2; the firstintermediate air pressure supply pipe, 238, from the discharge of thelow-pressure compressor stage, 2, to the intake of the medium-pressurecompressor stage, 3; the second intermediate air pressure supply pipe,239, from the discharge of the medium-pressure compressor stage, 3, tothe intake of the high pressure compressor stage, 4; the firstintermediate reacted gas pressure supply pipe, 241, from the dischargeof the high-pressure expander stage, 20, to the intake of themedium-pressure expander stage, 19; the second intermediate reacted gaspressure supply pipe, 240, from the discharge of the medium-pressureexpander stage, 19, to the intake of the low-pressure expander stage,18; the exhaust gas pipe, 30, from the low-pressure expander stage.These pipes constitute fixed open gas flow connections which remain openwhenever the plant is operating. Further additional connections shown inthe example of FIG. 1 are the high pressure steam supply connections,31, and steamflow control valves, 32, 33, for supply of combustion steamto be added to the air from compressor stages in order to supplyreactant gases containing both steam and oxygen into at least somecontainers. The connections between each container and manifold to eachcompressor stage and to each expander stage, and not shown in FIG. 1,are shown in FIG. 2 for but one of the containers, 11, and its manifold,242. The connections and valves, 8, 37, 38, 39, 40, 41, provide a meansfor connecting the containers, 11, to each of the expander stages, 20,19, 18, and to each of the compressor stages, 2, 3, 4, and in thatorder. Each of the containers, 11, 12, 13, 27, 28, 29, 34, are similarlyequipped with the changeable gas flow connections with valves, shown inFIG. 2 for container 11, to each compressor stage and to each expanderstage.

In the operation of the example multistage cyclic oxidation chargasifier plant shown in FIG. 1 and FIG. 2, each container is connectedin a sequence of gas flow connectings to the discharge end of eachcompressor stage and to the inlet end of each expander stage. Thissequence of gas flow connectings starts with the lowest pressure stageof the compressor, proceeds in turn through each next higher pressurestage of the compressor, and after the highest pressure compressorstage, continues to the highest pressure stage of the expander and thenproceeds in turn through each next lower pressure stage of the expander.After a container has proceeded through this full sequence, the sequencecan subsequently be repeated again and again. When pressure vesselcontainers are used for each container refueling and coke removal arepreferably timed to occur at the end of a sequence sometime betweendisconnecting from the lowest pressure expander stage and reconnectingto the lowest pressure compressor stage to start the next sequence, whenthe container is at minimum cycle pressure. The next sequence of gasflow connectings can then commence after refueling and coke removal arecompleted. For example, in FIG. 2 the foregoing sequence of connectingsfor container 11 can be carried out as follows: valve 8 is opened andvalve 37, 38, 39, 40, 41, are closed and container 11 is connected onlyto the discharge of the lowest pressure compressor stage, 2; after atime interval valve 8 is closed and concurrently valve 37 is opened andcontainer 11 is then connected only to the discharge of the next highercompressor stage, 3; after the next time interval 37 is closed andconcurrently valve 38 is opened and container 11 is then connected onlyto the discharge end of the highest pressure compressor stage, 4; afterthe next time interval valve 38 is closed and concurrently valve 41 isopened and container 11 is then connected only to the inlet end of thehighest pressure expander stage, 20; after the next time interval valve41 is closed and concurrently valve 40 is opened and container 11 isthen connected only to the inlet end of the next lower pressure expanderstage, 19; after the next time interval valve 40 is closed andconcurrently valve 39 is opened and container 11 is then connected onlyto the inlet end of the lowest pressure expander stage, 18; after thenext time interval valve 39 is closed and a sequence of gas flowconnectings has been completed; refueling and coke removal preferablytake place for container 11 after valve 39 is closed at the end of onesequence of gas flow connectings and before valve 8 is opened tocommence the next such sequence, or while these valves are being closedand opened. Such refueling need not occur between every pair ofsequences for a container, and when refueling is to be less frequent,the value of the refuel ratio, Z, is increased so that the number oftime periods actually utilized for refueling becomes less than thenumber of time periods available for refueling as described hereinafter.Similarly, coke removal need not occur between every pair of sequencesfor a container and less frequent coke removal can be achieved byincrease of the coke removal ratio, y, so that the number of timeperiods actually utilized for coke removal becomes less than the numberof time periods available for coke removal. Each of the othercontainers, 12, 13, 27, 28, 29, 34, also has similar connections andvalves to each compressor and expander stage and also is similarlyconnected in sequence to these stages and to refuel and coke removal inthe same manner as described for the one container, 11, except that eachcontainer follows out its sequence of connectings in a time orderdisplaced from that of all the other containers so that any onecompressor or expander stage is connected to but one container. So thateach stage will always have one container connected, the several activecontainers change gas flow connectings all at the same time and thus thetime interval between changes of gas flow connectings, tcc, is the sameas between different containers even though it may differ as betweendifferent time intervals in a sequence. The cycle time, tc, is thenequal to the product of the time interval between changes of gas flowconnectings, tcc, if constant, and the sum of the number of containersbeing compressed, nc, and the number of containers being expanded, nx,which sum, being the number of active containers, also equals the sum ofthe number of compressor stages and the number of expander stages.

    tc=(tcc)(nc+nx)

The cycle time, tc, is basically determined by how long it takes thecompressor to pump up a container from the selected value of minimumcycle pressure, PO, up to the selected value of maximum cycle pressure,PM, and clearly increases with increasing container gas space volume andwith decreasing compressor flow rate capacity, ma.

k. Various means for stopping the char gasifier plants of this inventioncan be used, such as:

a. Supply sufficient excess steam for stopping to containers beingcompressed so that the char fuel becomes chilled well below its rapidreaction temperature by the endothermic steam-char reaction.

b. Recirculate reacted gas, essentially free of oxygen gas, into the aircompressor intake and the oxidation gasification reactions cease due tolack of oxygen.

c. Where the compressor is separately driven it can simply be turnedoff.

An example of an excess steam stopping means is shown schematically inFIG. 7 and comprises a steam stopping valve, 243, which when openedfeeds excess steam into the containers, 11, 12, 13, undergoingcompression with air, via the metering orifices, 244, 245, 246, whichassures adequate excess steam into each container as to assure stopping.The valve 243 is only to be opened when the plant is to be stopped.

The foregoing elements are parts of the cyclic oxidation char gasifierportion of this example cyclic Velox boiler and operate to carry out apreferably complete burning of the char fuel inside the containers asfollows:

(1) As shown in FIG. 3 for the example container, 11, each container hasa volume of hot, porous char fuel, 43, inside and during the subsequenceof connections to compressor outlets, air is forced into the pores ofthe char fuel as the pressure rises and reacts therein with the hotcarbon to form principally carbon monoxide gas. When steam is alsoadmitted into containers during compression, those steam portions forcedinside the char fuel pores react therein also with the hot carbon toform carbon monoxide and hydrogen. Additional air is also compressedinto the dead volume, 44, of the container, 11, where no char fuel islocated and only very little of this air reacts with char fuel duringcompression.

(2) During the subsequence of connections to expander inlets, whichfollows next after the compressor subsequence, the reacted gases formedinside the char fuel pores expand out of these pores as the pressuredrops during expansion and react then further with the air previouslycompressed into the dead volume, 44, to form complete combustion gasescontaining carbon dioxide and water. Preferably sufficient air iscompressed into the dead volume 44, so that the carbon monoxide andhydrogen in the emerging pore gases can be burned essentially completelyto carbon dioxide and water. These complete combustion gases then flowthrough the stages, 20, 19, 18, of the expander engine, 17, doingmechanical work on the engine and leaving as exhaust gas via thedischarge, 30.

(3) Preferably the pressure rise of compression is made sufficient thatthe work done on the expander engine exceeds the work done by thecompressor upon the air and a net output work results which is absorbedby the power means, 42, such as an electric generator.

(4) Following the subsequence of connections to expanders, eachcontainer is disconnected from both the expander and the compressor fora time period available for refueling and a time period available forcoke removal, and these two time periods can be the same time period orcan be two successive time periods.

(5) A char and ash pile height sensor and control means, as shown forexample in FIG. 3, senses when this pile is above a certain height, ha,and also when this pile is below another certain height, hb, and actsupon the means for connecting the refuel transfer means, 45, to connectthe refuel transfer means to the container, 11, during the time periodavailable for refuel whenever the pile height is below the level, hb,and to disconnect the refuel transfer means whenever the pile height isabove the level, ha. In this way, the height of the coal and ash pile iskept essentially between these levels, ha, and hb; photoelectric cells,46, with collimators, 47, facing discrete light sources, 48, withcollimators, 49, are an example of such a height sensor.

(6) An ash pile height sensor and control means senses when the ash pileis above a certain height, 1a, and also when the ash pile is belowanother certain height, 1b, and acts upon the means for connecting thecoke removal transfer means, 50, to connect the coke removal transfermeans to the container, 11, during the time period available for cokeremoval whenever the ash pile height is above the level, 1a, and todisconnect the coke removal transfer means whenever the ash pile heightis below the level, 1b. In this way, the height of the ash pile, 51, iskept esssentially between these levels, 1a, and, 1b. Temperaturesensors, 52, are an example of such an ash pile height sensor since thenon-reactive ash pile, 51, is colder than the burning char volume, 43.

(7) These char and ash pile height sensor and control means thusfunction to maintain the char fuel volume, 43, the ash volume, 51, andthe dead volume, 44, approximately constant and between set limitswithin each of the containers.

The cyclic Velox boiler plant of FIG. 1 additionally includes a steamboiler, a steam superheater, and a steam reheater which comprises thefollowing:

j. Each of the containers, 11, 12, 13, 27, 28, 29, 34, is fitted with aradiant heater section positioned on the interior surface of eachcontainer as shown, for example, in FIG. 3 where several tubes, 53,secured to the inner surface of the pressure vessel wall, 54, of thecontainer, 11, comprise the radiant heater heat exchange surfaces.Preferably the tubes, 53, cover as much of the inner surface of thecontainer walls, 54, as possible as is shown in FIG. 4 which is across-section, as indicated, of FIG. 3. The several tube inlets, 55, areconnected together and to the radiant heater liquid water inlet, 56, andthe several tube outlets, 57, are connected together and to the radiantheater water outlet, 58. The radiant heater tubes, 53, are preferablyseparated from the ash pile, 51, by a covering of protective material,59, such as a ceramic. Each of the containers 11, 12, 13, 27, 28, 29,34, is similary fitted with a radiant heater section and with a radiantheater liquid water inlet, 56, and a radiant heater water outlet, 58.

k. For the particular cyclic Velox boiler plant shown in FIG. 1, theseseveral radiant heater sections are connected in parallel flow, so thatwhatever water flows through one of the radiant heaters does not flowthrough any other radiant heater during any one recirculation, byconnecting all water outlets, 58, to a common outlet pipe, 60, and byconnecting all water inlets, 56, via flow distributors, 61, to a commonliquid water inlet pipe, 62. The flow distributors, 61, assure that somewater is distributed to all radiant heaters and, for the example of FIG.1, distribute the water essentially equally to each radiant heater.

l. From a source of boiler feedwater, 63, the feedwater pump and drivemeans, 64, pumps liquid water into the common liquid water inlet pipe,62, against the boiler steam pressure. As this water flows through theseveral radiant heater sections, it is heated inside the tubes, 53, byradiation heat transfer from the burning char fuel pipe, 43, and byconvection when the complete combustion gases pass out of the containersduring expansion. This heating may cause some of the feedwater to boiland become steam, and this steam and any liquid water then flow out ofeach radiant heater and into the common water outlet pipe, 60.

m. A steam-liquid separator, 65, such as a steam drum, receives themixture of steam and liquid water from the radiant heater outlet pipe,60, via its inlet, 66, and separates the mixture into a steam portionwhich leaves via the steam outlet, 67, and a liquid water portion whichleaves via the liquid water outlet, 68.

n. A liquid water recirculator means, such as a natural circulationdowncomer or a forced recirculator pump and drive means, 69,recirculates liquid water from the separator, 65, back to the commonliquid water inlet pipe, 62, of the several radiant heaters.

o. A recirculating water convection preheater, 70, can be interposedbetween the recirculator, 69, and the radiant heater's common inlet, 62,to add additional heat to the recirculating water from the completecombustion gases leaving containers, such as container, 27, while theyare connected to the inlet, 21, of the lowest pressure expander stage,18, via their changeable gas flow connection thereto, 26.

p. A primary steam convection superheater, 71, can be heated by theexhaust gas leaving the discharge, 30, of the lowest pressure expanderstage, 18, to superheat the steam leaving the steam separator, 65, viaits steam outlet, 67.

q. A secondary steam convection superheater, 72, can be heated by thecomplete combustion gases leaving containers, such as container, 29,while they are connected to the inlet, 23, of the highest pressureexpander stage, 20, via their changeable gas flow connection thereto,24, to further superheat the steam leaving the primary superheater, 71,before passing the fully superheated steam to its final delivery outlet,73, to steam users such as a steam turbine engine.

r. A steam convection reheater, 74, can be heated by the completecombustion gases leaving containers, such as container, 28, while theyare connected to the inlet, 22, of the intermediate pressure expander,19, via their changeable gas flow connection thereto, 25, to reheatsteam returning via a pipe, 75, from users such as intermediate pressuresteam turbine stages and returning to lower pressure stages of the uservia a pipe, 76.

s. A feedwater convection heater, 77, can be interposed between thefeedwater pump, 64, and the common liquid water inlet pipe, 62, to theradiant heaters to heat the feedwater by the exhaust gases leaving theprimary steam superheater, 71, and flowing to the combustion gas exhaustpipe, 78.

t. A steam separator drum liquid level sensor, 79, and control, 80, cansense the liquid water level in the steam drum, 65, and control thefeedwater flow rate of the feedwater pump, 64, as by controlling thefeedwater pump drive means speed, to maintain an essentially constantliquid water level in the steam drum. In this way, the feedwater pump,64, functions to replace the steam removed from the boiler via the steamoutlet, 67.

u. A steam boiler pressure sensor, 81, and control, 82, can sense thesteam pressure in the steam drum, 65, and control the density of the airsupplied to the inlet, 14, of the first compressor stage, 2, bycontrolling the air precompressor, 15, as by controlling the speed ofthe air precompressor drive motor, 16, so that as boiler pressuredecreases below a set value, the air density at the inlet, 14, isincreased and as boiler pressure increases above a set value, the airdensity at the inlet, 14, is decreased. Increase of air density atcompressor inlet increases the char fuel burn rate by increasing eitherthe maximum air pressure achieved inside containers during compressionor by shortening the time required to reach a set value of maximumcompression pressure, and this increased burn rate also increases steamboiling rate by increasing heat transfer from the char fuel and completecombustion gases to the water and steam inside the radiant heaters.Decrease of air density similarly decreases char fuel burn rate andhence steam boiling rate. In this way, the steam pressure in the boilersteam drum, 65, can be maintained essentially constant between setvalues by action of the steam boiler pressure sensor, 81, and control,82, upon the compressor inlet air density setting means compressor, 15,and drive means, 16. It is then at this pressure that boiling takesplace within the boiler means of this invention. Where very low steamboiling rates are occasionally to be used, the air precompressor, 15,can be supplemented with an intake throttle valve, 83, controlled via asupplemental control, 84, so that air density at compressor inlet, 14,can be less than atmospheric air density at the air intake, 85, ifnecessary.

v. An intercooler, 86, may sometimes be used to cool down theprecompressed air leaving the precompressor, 15, before it reaches thecompressor inlet, 14, in order to further increase the air density.Atmospheric air or cooling water are examples of cooling media to usefor this intercooler, 86.

These boiler elements of this example cyclic Velox boiler operate togenerate steam and to cool down the complete combustion gases of thecyclic oxidation char gasifier as follows:

(8) The complete combustion gases formed inside the containers, such as27, 28, 29, while they are undergoing expansion, pass along the tubes,53, of the radiant heaters and through the gas sides of the secondarysteam superheater, 72, the steam reheater, 74, and the recirculatingwater preheater, 70, and are cooled by transfer of heat from thecombustion gases through the walls of the tubes, 53, and through thewalls of the other heaters into the water on the steam side of thesevarious heat exchangers. In consequence these combustion gases can besufficiently cooled in this way as to be safely admitted into presentlyavailable expander engine inlets without damaging the engine. By coolingthe complete combustion gases in this way, we need only use an excessair amount inside the containers sufficient to achieve essentiallycomplete burning of the char fuel to carbon dioxide and water. Thus, noadditional excess air is needed for the purpose of cooling thecombustion gases down to a safe value of expander inlet temperature. Inconsequence, the compressor and expander losses due to use of excess airfor cooling are avoided and the efficiency of net power production bythe cyclic Velox boiler can thus be greater than that of a conventionalcombined cycle gas turbine engine. This is one of the beneficial objectsof this invention.

(9) The steam generated by a cyclic Velox boiler can be used for any ofvarious purposes but is especially well suited for use with a steamturbine engine power cycle to generate additional work output. In thisway, a combined cycle power plant is created by using a cyclic Veloxboiler of this invention which can burn lump coal or other char fuel ina fixed fuel bed without ash particle carryover into the expanderengine. Fuel bed channeling problems of usual steady pressure fixed fuelbed coal burners are avoided since the char fuel burns inside its poresduring compression with air. These abilities of a cyclic Velox boiler toburn lump coal in a fixed bed without ash particle carryover and withoutfuel bed channeling problems are additional beneficial objects of thisinvention.

(10) Refueling of containers and ash removal therefrom are preferablycarried out only when the containers are not connected to either thecompressor or the expander. As a result, the pressure inside thecontainer at refuel and coke removal can be low and essentiallyatmospheric, thus reducing the problems of operation and maintenance ofthe refuel transfer means and the coke removal transfer means ascompared to those encountered with containers operated at high andsteady pressures. This low pressure refueling and ash removal are stillanother beneficial object of this cyclic Velox boiler invention.

(11) The steam separator, 65, and recirculator, 69, scheme shown in FIG.1 will often be preferred as relatively simple, with radiant heatersconnected in parallel and with a high flow rate of water recirculation.With this scheme, the flow rate can be essentially equal to each radiantheater and adjustment of the flow distributors, 61, is not needed. Butsuch separator and recirculator systems can only be used at steam boilerpressures sufficiently below the critical pressure of water that thedensity difference between liquid water and steam is sufficient thatseparation can be accomplished in the separator means, such as a steamdrum, 65. At steam boiler pressures near or above the critical pressureof water, such steam separator and liquid recirculator schemes cannot beused.

Another particular example of a cyclic Velox boiler plant is shownschematically in FIG. 5 and comprises:

a. The single stage air compressor, 87, with drive motor, 88, compressesair from its inlet, 89, via its outlet, 90, into the container, 91,being compressed via its changeable gas flow connection, 92.

b. The single stage expander, 93, with power absorbing generator, 94,receives complete combustion gases into its inlet, 95, from thecontainer, 96, being expanded via its changeable gas flow connection,97, and exhausts fully expanded gases via its exhaust, 98.

c. When the container, 91, is fully compressed to the set value ofmaximum compression pressure, the two containers, 91, and, 96, exchangefunction by closure of the changeable gas flow connections, 92, and, 97,and opening of the changeable gas flow connections, 99, and, 100, andthe next time period commences at the end of which the containers, 91,96, again exchange function.

d. Where only two containers are used as shown in FIG. 5, refueling andash removal can occur at small pressures as, for example, by refuelingand removing ashes, following expansion during the early part ofcompression when pressures are not yet very high.

e. The containers, 91, 96, are fitted with radiant heater sectionspositioned on the interior surface of each container, as shown, forexample, in FIG. 3 and described hereinabove, and with radiant heaterliquid water inlets, 101, 102, and radiant heater water outlets, 103,104.

f. From a source of boiler feedwater, 105, the feedwater pump and drivemeans, 106, pumps liquid water against the boiler steam pressure intothe liquid water inlet, 101, of the radiant heater inside container, 91,via the changeable water flow connection, 107.

g. The steam superheater section, 108, receives steam from the radiantheater section inside containers, 96, or, 91, via its water outlet, 104,or, 103, and the changeable water flow connection, 109, or, 114, anddischarges superheated steam to users via the steam delivery pipe, 110.

h. Other changeable water flow connections, 113, 115, are opened so thatthe water pumped by the feedwater pump, 106, into the radiant heaterinside container, 91, flows from its outlet, 103, via the changeablewater flow connections, 115, and, 113, into the liquid water inlet, 102,of the radiant heater inside container, 96.

i. At the start of the second time period when the changeable gas flowconnections, 92, 97, are closed and, 99, 100, opened so that container,96, is being compressed while container, 91, is being expanded,concurrently the changeable water flow connections, 107, 113, 109, 115,are closed and the changeable water flow connections, 112, 116, 111,114, are opened. In this way, the two radiant heaters are alwaysconnected in series and with the feedwater flowing into that radiantheater inside the container being compressed and with steam flowing outof that radiant heater inside the container being expanded.

j. The changeable gas flow connections, 92, 97, 99, 100, and thechangeable water flow connections, 107, 109, 111, 112, 113, 114, 115,116, are thusly concurrently opened and closed by means for opening andclosing which are controlled by a control means. The gas flow and steamflow connections can be thusly changed at fixed time intervals in whichcase the control means can be a timer. Alternatively, the gas flow andsteam flow connections can be thusly changed whenever the containerbeing compressed reaches a set value of maximum pressure in which casethe control means comprises a pressure sensor and control meansoperative upon the means for opening and closing the changeable gas flowconnections, such as is described hereinafter. Other control schemes canalso be utilized.

k. When the radiant heaters are thusly connected in series, theindividual tubes or water passages on the steam side of a single radiantheater may also be connected in series. Alternatively, the individualtubes or water passages on the steam side of a single radiant heater maybe connected in parallel. When the several tubes of a single radiantheater are thusly connected in parallel flow distribution adjustors maybe preferred on the tubes to obtain an essentially equal distribution ofwater between the several tubes in parallel. An example of such flowadjustors, 117, 118, 119, 120, is shown schematically in FIG. 6 forseveral radiant heater tubes, 53, only some of which are shown partiallyin this FIG. 6. These flow adjustors, 117, 118, 119, 120, can be handadjusted to secure the desired degree of equality of water flow intoeach of the tubes, 53, of the single radiant heater.

The operation of the FIG. 5 example cyclic Velox boiler plant isessentially similar to that already described for the cyclic Veloxboiler plant of FIG. 1, the important difference being the water flowpattern through the radiant heater section, as described above, and theabsence of a steam separator and liquid recirculator. Hence, the steamboiler of FIG. 5 is a once-through type of boiler and can be used atboiler steam pressures near and above the critical pressure of watersince a density difference between the liquid water and the steam insidethe boiler is not needed for proper operation of this boiler type.

In the majority of applications of cyclic Velox boilers, completecombustion of the char fuel to carbon dioxide will be preferred asdescribed in the foregoing example plants. In some applications,however, only gasification of the char fuel to carbon monoxide or, ifcombustion steam is used, to carbon monoxide and hydrogen, will bedesired. This gasification only result can be readily achieved by havingthe containers fully occupied with porous char fuel. Thus, with noappreciable dead space inside the containers for holding secondary air,the secondary burning reaction of carbon monoxide and hydrogen emergingfrom the char pores during expansion will not occur and only thegasification reaction will take place.

Char fuel burning via the cyclic compression and expansion used in thisinvention utilizes substantially all of the internal pore area of thefuel for carrying out burning. As a result, very high burn rates can beobtained from moderately sized fuel volumes. This high burn rate perunit volume is much greater than can be achieved on grates where burningoccurs largely on only the external area, rather than the pore area, ofthe char fuel chunks. This is another beneficial object of thisinvention that very high char fuel burn rates per unit volume can beachieved.

D. Details of various elements

Combustion steam can be used in cyclic oxidation char gasifiers as ameans of controlling expander inlet temperatures to safe values butcannot be used for this purpose when complete combustion of the charfuel is taking place in the containers. Nevertheless, combustion steamcan be useful with complete char combustion as a means of adjusting thedistribution of heat transfer between the radiant heaters and thoseconvection heaters on expander inlets. As combustion steam flow isincreased relative to air flow into containers, less energy is releasedby the primary reaction to carbon monoxide and hydrogen inside the charpores, and more energy is released by the secondary reaction to carbondioxide and water outside the char pores. As a result, radiation heattransfer is reduced and convection heat transfer increased when thesteam to oxygen ratio of the reactant gases going into the containers isincreased. This heat transfer distribution control can be used invarious ways as, for example, for control of final steam superheattemperature. For example, the secondary steam superheater, 72, of FIG.1, can experience greater heat transfer and hence produce higher steamsuperheat when the flow of combustion steam into containers, 12, 13,which are being compressed by the higher pressure stages, 3, 4, of thecompressor, 1, via the delivery means, 32, 33, is increased. In similarfashion steam superheat can be reduced by decreasing the flow ofcombustion steam. An example of one means for controlling steamsuperheat is shown diagrammatically in FIG. 7 and comprises a steampressure regulator, 182, which sets the pressure of combustion steamfrom a high pressure steam source, 31, acting on the delivery orifices,32, 33, which deliver steam into the connected containers, 12, 13.Usually, the steam source will be the cyclic Velox boiler itself butother sources could be used. As the steam pressure is increased, moresteam is delivered and vice versa. The steam flowing into any one of theconnected containers, and hence the steam to oxygen ratio, is determinedin part by the area of the delivery orifice and in part by the upstreamorifice pressure set by the pressure regulating valve, 182, more steamflowing at larger areas and higher pressures. The orifices, 32, 33, canbe differently sized in order to achieve either an essentially constantsteam to oxygen ratio during compression with oxygen containing gases oran increase in steam to oxygen ratio as container pressure increases. Avapor pressure temperature sensor, 183, is located in the outlet, 73, ofthe final superheater, 72, and acts via the sealed bellows, 184, spring,185, and link, 186, to open the increase valve, 187, when superheatedsteam temperature is too low, and to open the decrease valve, 188, whensuperheated steam temperature is too high, these two valves being springclosed. The steam pressure regulating valve, 182, functions to maintainits downstream pressure upon the orifices, 32, 33, essentially equal tothe pressure applied by a regulating gas to its regulating chamber, 190.The increase valve, 187, when open admits high pressure regulating gasfrom a source, 191, via an orifice, 192, to the regulating chamber, 190,and thus acts to increase steam pressure on the orifices and hence actsto increase steam flow rates and to increase superheated steamtemperature. The decrease valve, 188, when open bleeds gas out of theregulating chamber, 190, via an orifice, 193, and thus acts to decreasesteam pressure on the orifices and hence acts to decrease steam flowrates and decrease superheated steam temperature. In this way, thecontrol scheme of FIG. 7 functions to control superheated steamtemperature. A vapor pressure temperature sensor, 183, is shown in FIG.7 but other temperature sensors, such as thermocouples with electricalcontrol circuits, gas pressure sensors, or bimetallic temperaturesensors, could alternatively be used. A hand-adjusted steam pressureregulating valve could be substituted for the automatic steam pressureregulating valve shown in FIG. 7, when hand control of superheated steamtemperature was preferred. In general, for superheated steam control, weseek to control the combustion steam flow into those reactant gaseswhich will subsequently flow as combustion gases through the steamsuperheater. For this FIG. 1 example case, it is the air and steam whichlast enter the containers from the outlet, 7, of the highest pressurecompressor stage which will subsequently first enter the high pressureexpander stage, 20, via the gas side of the final steam superheater, 72.

Where a steam reheater is used at one of the expander inlets, thecombustion steam can also be used as a means of controlling the finaltemperature of the reheated steam. For example, the reheater, 74, ofFIG. 1 is heated by expanding combustion gases leaving that container,which is connected to the second stage, 19, of the expander, 17. Theseparticular expanding combustion gases will contain the air and steamcompressed originally into char pores while a container was connected tothe second compressor stage, 3, provided that the number of compressorstages equals the number of expander stages as shown in FIG. 1 and thatthe pressure rises per compressor stage correspond about equally andsymmetrically with the pressure drops per expander stage. Hence, ascombustion steam flow is increased through steam delivery means, 32,more heat is transferred via the convector, 74, and reheated steamtemperature is increased. The opposite effects occur when combustionsteam flow is decreased. In general for reheated steam temperaturecontrol, we seek to control the combustion steam flow into thosereactant gases which will subsequently flow as combustion gases throughthe steam reheater. For the FIG. 1 example case, it is the air and steamwhich enter the containers from the outlet, 6, of the intermediatepressure compressor stage, 3, which will subsequently enter theintermediate pressure expander stage, 19, via the gas side of the steamreheater, 74. The steam flow controller for this reheat control can besimilar to that described for superheat control if separate therefrom.Alternatively, an orifice area proportioning scheme can be used toproportion combustion steam flow between those gases going into thesuperheater and those gases going into the reheater.

A refuel mechanism is needed as a means for adding fresh char fuel intothe container to replace that gasified. A wide variety of devices can beused as this refuel mechanism and several of these are described in thecross-referenced related application. An example of a pneumaticallyactuated refuel mechanism is shown in FIG. 3 as mounted on the top ofthe sealed pressure vessel container, 11, and connecting a fresh charfuel supply hopper, 247, to said container. This example pneumaticrefuel mechanism comprises a refuel valve, 45, a refuel piston, 248,working in a refuel cylinder, 249, within the refuel valve body, apneumatic pressure supply hole, 250, and pressure sealing means, 251.Not shown in FIG. 3 are, a means for rotating the refuel valve body, 45,through an arc of 180 degrees about a horizontal axis, as by hand orautomatically via a pneumatically actuated crank, and a control valve tocontrol admission and release of high pressure pneumatic gas via thepressure supply hole, 250, to the refuel cylinder, 249, where the gaspressure can act on the refuel piston, 248. As shown in FIG. 3, therefuel valve, 45, has positioned the refuel piston, 248, in contact withthe supply hopper, 247, so that, by release of pressure from the refuelcylinder, 249, a charge of fresh char fuel will enter the refuel valveunder the action of the weight of the loose char fuel in the supplyhopper. When refueling is to take place, the refuel valve, 45, isrotated through a 180 degree arc to position the refuel piston incontact with the interior of the container, 11, and refueling isaccomplished by application of pneumatic pressure to the refuel piston,248, via the pressure supply hole, 250, from the control valve, thispressure then causing the refuel piston, 248, to force the fresh charfuel into the container, 11. When refueling is completed the refuelvalve, 45, is rotated through a 180 degree arc to return it to theposition shown in FIG. 3 where the pressure sealing means, 251, sealsthe refuel end of the container, 11, against gas leakage. Preferably,the above-described refueling process is carried out when the containeris at minimum cycle pressure in order to minimize gas leakage from thecontainer and, with this preferred refuel timing, compressed reactantgas or reacted gas can be used as the source of high pressure pneumaticgas for actuation of the refuel mechanism. Alternatively, other sourcesof high-pressure gas can be used for actuation or hydraulic actuationcan be used also. The refuel mechanism shown in FIG. 3 can refuel with achar volume equal to the maximum displacement of the refuel piston, 248,in the refuel cylinder, 249. This maximum displacement of each refuelmechanism is at least equal to the maximum required char refuel volume.

While the time interval between refuelings, tf, can in principle havealmost any value, it is usually preferable to refuel each container whenit is at minimum cycle pressure at the end of an expansion and beforestarting the next compression in order to minimize leakage of reactantand reacted gases. Hence, we prefer to refuel each container at mostonce for each cycle of compression followed by expansion and for thiscase the refuel time interval, tf, is determined by the cycle timeinterval, tc, for carrying out one full cycle of compression andexpansion on one container, and the number of active containers, na,equal to the sum of the number of containers being compressed, nc, plusthe number of containers being expanded, nx. ##EQU1## Wherein the refuelratio Z is any positive integer. The total number of containers, nt, mayexceed the number of active containers, na, by at least one so that theinactive containers can be refueled, and have coke removed, if desired,in a leisurely manner and at low pressures of the containers, beforebeing returned again to an active cycle of compression followed byexpansion. Of course, for an oxidation gasifier, refueling and cokeremoval cannot be too leisurely or the char fuel within a container willcool down below its rapid reaction temperature. For any one containerthe time interval between refuelings, tfl, for this case with extra,inactive containers, is then the product of the total number ofcontainers, nt, and the time interval between refuelings, tf.

Various methods of controlling the initiation of refueling can be used.For example, the disconnecting of a container from the last stage of theexpander could initiate the refuel mechanism to carry out one refuelingoperation, and in this case the integer, Z, would be one. Where valuesof Z other than one are to be used, a mechanical or electrical countercan count up the number of compression and expansion cycles eachcontainer experiences. When the set number of cycles, which equals Z, isreached the counter then initiates the refuel mechanism when thecontainer disconnects from the last stage of the expander, and resetsitself to start counting cycles again. The set number of cycles, andhence Z, can be made adjustable in integral steps and provides a meansfor adjusting the maximum char refueling rate available. Other methodsof initiating the refuel mechanism can also be used.

One example means for connecting the refuel mechanism is shown in FIG. 8and comprises the refuel shaft, 135, which rotates the refuel valve, 45,of FIG. 3, the refuel shaft gear, 136, driven by the refuel lever andgear, 137, which is, in turn, driven by the piston, 138, and cylinder,139. The arc of motion of the refuel lever, 137, between the stops, 140,141, and the pitch diameter ratio of the refuel shaft gear, 136, and thelever gear, 137, are selected to assure that the refuel shaft, 135, andhence the refuel valve, 45, are rotated through a half turn when therefuel lever, 137, moves from the stop, 140, to the stop, 141. Themoving port, 142, rotates with the refuel gear, 136, and connects viathe passage, 143, in the shaft, 135, to the driving side of the refuelpiston, 248, of FIG. 3, and connects at its other end either to theatmospheric vent, 144, as positioned in FIG. 8, or to the high pressuredriving gas supply via the passage, 145, when rotated a half turn aswhen the lever, 137, is against the stop, 141. As shown in FIG. 8, therefuel shaft, 135, and the refuel valve, 45, are in the disconnectedposition shown in FIG. 3 with char fuel from the hopper, 247, reloadinginto the refuel valve, 45, and the side, 146, of the piston, 138, isvented to atmosphere via the valve, 147, and the side, 148, of thepiston, 138, is connected to the high pressure driving gas via thevalve, 147, and the pipe, 149, thus holding the lever, 137, against thestop, 140. To connect the refuel mechanism the refuel solenoid, DRF, isenergized via the electrical connection, T2, and the refuel interrupterswitch, 121, thus rotating the valve, 147, through a quarter turnagainst the return spring, 150, and applying high pressure to the side,146, of the piston, 138, and atmospheric pressure to the side, 148, ofthe piston, 138, so that the piston, 138, moves the lever, 137, againstthe stop, 141, thus rotating the refuel valve, 45, into the refuelingposition and also applying high pressure driving gas via the passage,145, to the refuel piston, 248, so that fresh char fuel is forced intothe container, 11. When the refuel solenoid, DRF, is next de-energizedthe pressures on the piston, 138, are again reversed and the piston,138, lever, 137, shaft, 135, are all returned to their position shown inFIG. 8, and a refueling process has been completed. A refueling processmay be thusly carried out by hand via the switch, 156, or preferablyautomatically via the connection, T2, from the cycle time intervalcontroller to be described hereinafter. The hand switch, 156, can beused during startup to fill the container with char fuel by repeatedlycarrying out refuel processes. The refuel interrupter switch can beopened and closed by the char fuel and ash pile quantity sensor andcontrol means shown schematically in FIG. 9 whose upper limit sensorinput, 122, is from the char fuel pile upper sensor, 46, at ha of FIG.3, and whose lower limit sensor input, 123, is from the char fuel pilelower sensor, 46, at hb of FIG. 3. Thus, when the coal and ash pileinside the container, 11, is above the upper limit, ha, the controller,124, opens the interrupter, 121, and the refuel transfer means will notbe connected to the container during refuel intervals. When the coal andash pile drops below the lower limit, hb, the controller, 124, closesthe interrupter, 121, and the refuel transfer means will then beconnected to the container and refueling will occur whenever thatcontainer reaches a refuel time interval. In this way, the coal and ashpile quantity sensor and control means shown in FIGS. 3, 9, and, 8,functions to keep the coal and ash pile height between the upper limit,ha, and the lower limit, hb. Electric power is supplied to the sensors,controller and interrupter via the connections, 125.

A coke removal mechanism can also be used with oxidation gasifiers whereit is desired to remove partially oxidized char fuel from the containersas a coke product output. Even for those oxidation gasifiers where theinput char fuel is to be fully oxidized to gases, a coke removalmechanism will still be needed in most cases with sealed pressure vesselcontainers as a means for removing the ashes and is then an ash removalmechanism. Whether used for removal of partially oxidized char, or fullyoxidized ashes, all such mechanisms are herein and in the claimsreferred to as coke removal mechanisms and constitute a means forremoving a volume of solid materials from the containing means. A widevariety of devices can be used as this coke removal mechanism andseveral of these are described in the cross-referenced relatedapplications wherein they are called ash removal mechanisms. Where charfuels of extremely low ash content are to be fully oxidized, ash removalcan be carried out by hand whenever the plant is shut down but such acoke removal means limits the plant to only such char fuels of whichthere are very few. Usually, a coke removal means will be preferredcapable of removing ashes while the plant is operating. An example of apneumatically actuated coke removal mechanism is shown in FIG. 3 asmounted on the bottom of a sealed pressure vessel container, 11, andconnecting the container interior to a coke discharge pipe, 252. Thisexample pneumatic coke removal mechanism comprises a removal valve, 50,a removal piston, 253, working in a removal cylinder, 254, within theremoval valve body, a pneumatic pressure supply hole, 255, and pressuresealing means, 256. Not shown in FIG. 3 are, a means for rotating theremoval valve body, 50, through an arc of 180 degrees about a horizontalaxis, as by hand or automatically as via a pneumatically actuated crank,and a control valve to control admission and release of high pressurepneumatic gas via the pressure supply hole, 255, to the removalcylinder, 254, where the gas pressure can act to move the removalpiston, 253. This example pneumatic coke removal mechanism is similar tothe aforedescribed refuel mechanism and the similarly named componentsfunction in a similar manner except that the coke removal mechanismremoves a volume of material from the container interior whereas therefuel mechanism adds a volume of material to the container interior.

Just as for refueling we also prefer to remove coke only when thecontainers are at minimum cycle pressure and hence, for this preferredcase, the time interval between coke removals, tfr, is given by thefollowing relation, similarly to that for the corresponding preferredrefuel time interval, tf. ##EQU2## Wherein the coke removal ratio y isany positive integer.

For oxidation gasifiers the coke removal mechanism can function toremove partially oxidized char fuel as an output coke product, ifdesired, or alternatively can remove only the ashes when the char fuelinput is to be fully oxidized to gaseous products.

Just as for the refuel mechanism, various methods of controlling theinitiation and timing of coke removal can be used. As a preferredexample case coke removal occurs only when the containers are at minimumcycle pressure and following next after a refueling. In this preferredway, gas leakage is minimized and the force of refueling acts to forceashes into filling the coke removal mechanism just before coke removaltakes place.

Where only ashes are to be removed, the mass and volume of ashes to beremoved by the coke removal mechanism are much smaller than the mass andvolume of char fuel to be refueled by the refuel mechanism. This volumedifference could be accommodated by designing the coke removal mechanismof a smaller size than the refuel mechanism, but then a gasifier soequipped would be impractical to utilize subsequently for production ofpartially oxidized coke product. When operating with full char oxidationto ashes, the actual coke removal rate can be reduced to the ashformation rate by reducing the frequency of coke removal relative to thefrequency of refueling. For the particular example refuel and cokeremoval mechanisms shown in FIG. 3 and for preferred coke removal andrefuel occurring only at minimum cycle pressure, the aforedescribeddecrease of coke removal frequency can be accomplished by increasing theinteger, y. This control of y can be done by hand or preferablyautomatically as ashes accumulate. For example, ash level sensor schemescan be used, as described in the cross-referenced related application,to sense when the ash level is well inside the container from the cokeremoval mechanism and this sensing signal can then cause a coke removalprocess to take place just after the next refueling process. In thisway, ash removal occurs automatically and in a manner to assure thatonly fully oxidized ashes are removed. Thermocouple temperature sensors,52, are shown in FIG. 3 as an example ash level sensor to detect whenthe ashes have accumulated up to the levels of these thermocouples, andhence are well above the coke removal mechanism, by sensing the drop intemperature when the adjacent solid ashes are no longer reacting becauseit has been as fully oxidized as possible. The coke removal interrupter,131, and control can be used and can operate similarly to the refuelinterrupter and control of FIG. 9 except that the sensor inputs are fromthe upper ash pile sensor, 52, at 1a of FIG. 3, and the lower ash pilesensor, 52, at 1b of FIG. 3. In a manner similar to the action of thecoal and ash pile quantity sensor and control, the ash pile quantitysensor and control functions to keep the ash pile level between theupper limit, 1a, and the lower limit, 1b.

Each container can be fitted with a refuel mechanism and a coke removalmechanism, as is shown for example in FIG. 3, or alternatively allcontainers can be refueled and have coke removed by use of one or a fewrefuel mechanisms and one or a few coke removal mechanisms which areconnected, in turn, to the containers when refueling and coke removalare to occur. Each container in this case would be fitted with a meansfor sealing the refuel port and the coke removal port when these werenot in use. The step of initiating a refuel or coke removal process fora container or of connecting the container to a refuel or coke removalmechanism for this purpose is herein and in the claims referred to asconnecting to a refuel or coke removal mechanism.

The interrupter switches, 121, 131, can be placed in the refuelsolenoid, RF, circuits and in the coke removal solenoid, CR, circuits ofthe control means for controlling the means for opening and closing thechangeable gas flow connections and for controlling the refuelconnecting means and the coke removal connecting means shownschematically in FIGS. 10 and 11.

One example scheme for control of cycle time is shown schematically inFIGS. 10 and 11. A char gasifier plant comprising a two-stage compressorand a two-stage expander is used for FIG. 10 and comprises sixcontainers, A, B, C, D, E, F, with two containers connected to the twocompressor stages, with two containers connected to the two expanderstages, with one container being refueled and with one container havingcoke removed during any one time period in the sequence of time periodsof open gas flow connections. Each container is fitted with a pressureactuated switch, SA, SB, SC, SD, SE, SF, which closes when the gaspressure inside the container reaches the intended value of maximumcompression pressure, PM. Each container is fitted with four changeablegas flow connections, a refuel mechanism connection, and a coke removalmechanism connection so there are twenty-four changeable gas flowconnections, six refuel mechanism connections and six coke removalmechanism connections. These connections for container, A, are shownschematically in FIG. 10 as follows:

AC1, changeable gas flow connection to the lowest pressure compressorstage;

AC2, changeable gas flow connection to the highest pressure compressorstage;

AX1, changeable gas flow connection to the highest pressure expanderstage;

AX2, changeable gas flow connection to the lowest pressure expanderstage;

ARF, refuel mechanism connecting means;

ACR, coke removal mechanism connecting means.

These same changeable gas flow connections and refuel mechanismconnections and coke removal mechanism connections for the other five(5) containers are also shown on FIG. 10 and are similarly designatedexcept the first designator letter is changed to correspond to thecontainer designator. For the example scheme of FIG. 10, the changeablegas flow connections are opened by applying electric power to a solenoidopened valve and these valves are closed by a closing spring. The refuelmechanism and the coke removal mechanism are also solenoid initiated asshown, for example, in FIGS. 8 and 9. Thus, when electric power from thesolenoid power source, SP, is applied to the terminal T1 of FIG. 10, thecontainers will then be connected as follows:

Container A open gas flow connected to the delivery end of the lowestpressure compressor stage;

Container B open gas flow connected to the delivery end of the highestpressure compressor stage;

Container C open gas flow connected to the inlet end of the highestpressure expander stage;

Container D open gas flow connected to the inlet end of the lowestpressure expander stage;

Container E connectable to refuel mechanism if refuel interrupter, 121,is closed;

Container F connectable to coke removal mechanism if coke removalinterrupter, 131, is closed.

By applying the solenoid power source, SP, for a time period to each ofthe terminals T1, T2, T3, T4, T5, T6, and in that sequence, it can beseen that each of the containers shown in FIG. 10 will be carriedthrough the desired sequence as follows:

a sub sequence of time periods of open gas flow connections to eachdelivery end of each stage of the compressor in order of increasingstage delivery pressure;

a sub sequence of time periods of open gas flow connections to eachinlet end of each stage of the expander in order of decreasing stageinlet pressure;

a time period connectable to the refuel mechanism;

a time period connectable to the coke removal mechanism;

and this sequence can be repeated by repeating the application of thepower source, SP, to the terminals, T1, T2, T3, T4, T5, T6. Note alsofor the wiring diagram as shown in FIG. 10 that each container is openedto only one stage during any one time period and that each delivery endof each stage of the compressor and each inlet end of each stage of theexpander has an open gas flow connection to a container during all timeperiods, provided that only one of the terminals, T1, T2, T3, T4, T5,T6, receives power during any one time period. The solenoid powersource, SP, is applied to each of the terminals, T1, T2, T3, T4, T5, T6,in turn, and one at a time in that sequence, by action of the pressureswitches, SA, SB, SC, SD, SE, SF, via the cascaded relays shownschematically in FIG. 11, wherein only three, R1, R2, R3, of the sixcascaded relays are shown.

Each cascade relay, such as R1, comprises a single coil solenoid switch,S1, with upper switch terminals, 257, closed when energized and withlower switch terminals, 258, closed when deenergized, and a double coilsolenoid switch, D1, with two separate switch terminals, 259, 260,closed when energized, switch terminals, 257, 259, and 260 being springopened. As shown in FIG. 11, the terminal T1 is connected to SP via theterminals, 261, of single coil switch, S2, and the switch terminals, 260and one coil of D1 and the coil of S1 are also energized thusly. Duringthe time period when T1 is thusly energized from SP, it is container Bwhich is being pumped up to maximum compression pressure, and it is thepressure switch, SB, on container B which is connected to the doublecoil switch, D2, of cascade relay R2 via switch terminals 259 and 257.When container B reaches the value of maximum compression pressure, PM,set into the pressure switch, SB, this switch closes and applies powerfrom source PP to one coil of the double coil switch D2 which thuscloses switches, 262, 263, energizes single coil switch, S2, and closesswitch terminal, 264, and opens switch terminals, 261, and disconnectssolenoid power source SP from terminal T1, and then connects solenoidpower source SP to terminal T2. A first time period of the sequence willthus end and the next time period commence during which container B willnow be connected to the highest pressure expander stage and it will becontainer A, now connected to the highest pressure compressor stage,whose pressure switch, SA, will next act to end the time period. Whensingle coil switch S2 was energized and switch terminals 261 wereopened, the double coil switch D1 and the single coil switch S1 weredeenergized, thus opening switch terminals 259, 260, and 257 and thusthe pressure switch, SB, is also disconnected, but the double coilswitch D2 is now energized via the switch terminals 263 and the switchterminals, 265, of single coil switch S3 of relay R3. Accordingly,cascade relay R2 is now arranged during the second time period in thesame way as cascade relay R1 was during the first time period and thuswhen container A is pumped up to the set value of maximum compressionpressure, the same events will take place and thus disconnect power fromT2, apply power to T3, disconnect pressure switch SA, connect pressureswitch SF, and thus change over to a third time period. The cascaderelay system shown in FIG. 11 thus applies solenoid power to theterminals T1, T2, T3, T4, T5, T6, in turn and in that sequence and,since cascade relay R6 connects similarly into cascade relay R1, thissequence of connections is repeated again and again. In this way, thedesired sequence of open gas flow connectings and refuel and cokeremoval connectings is carried out for each container, and is repeated,and each container is brought up to the desired maximum pressure ofcompression before being expanded. The desired maximum pressure ofcompression is set by adjusting, as by hand, the closing pressures ofthe several pressure switches SA, SB, SC, SD, SE, SF. For startup apressure switch bypass switch, SS, can set any one of the cascaderelays, say R3, and when the compressor and expander are started up, thesequence can commence soon thereafter. A wide variety of cascade relaysystems and pressure switch systems can also be used to carry out thedesired sequence and FIGS. 10 and 11 are only intended as a typicalillustrative example. Electronic control schemes can be substituted forthis cascade relay scheme as is well known in the art of electroniccontrols.

The aforedescribed scheme for control of cycle time is seen to comprisethe following:

a. means for opening and closing the changeable gas flow connections, inthe form of the solenoids and return springs on the valves such as AC1,AC2, BX1, BX2, etc., together with the solenoid power source, thepressure switches, and the cascade of relays;

b. means for connecting and disconnecting the refuel mechanism, in theform of the refuel initiating solenoids, such as ARF, and connectedlinkage, together with the solenoid power source and the refuelinterrupter switch and control;

c. means for connecting and disconnecting the coke removal mechanism, inthe form of the coke removal initiating solenoids, such as ACR, andconnected linkage, together with the solenoid power source, and the cokeremoval interrupter switch and control;

d. means for controlling the above means for opening and closing andmeans for connecting and disconnecting so that each container goesthrough the desired sequence of open gas flow connections, and timeperiod for refueling, and time period for coke removal, in a continuousseries of time periods, and so that each compressor stage delivery andeach expander stage inlet always has a container connected, in the formof the grouping of the solenoids connected to the terminals T1, T2, T3,T4, T5, T6, and the cascade of relays.

Where a constant cycle time is preferred, the aforedescribed scheme canbe modified by replacing the pressure switches and cascade relays by amotor-driven switch which directs electric power to the terminals T1,T2, T3, T4, T5, T6, in the desired sequence. The speed of the switchdrive motor can then be adjusted so that the desired maximum pressure ofcompression is reached. This motor speed adjustment can be done by handor automatically.

One example pneumatic-hydraulic scheme for control of cycle time isshown schematically in FIGS. 16 and 17. In lieu of the solenoid operatedchangeable gas flow connections of the FIG. 10 and 11 cycle time controlscheme, pneumatically operated valves are used for AC1, BC2, CX1, DX2,etc., of which only one, say AC1, is shown in FIG. 16. The valve, 266,is opened or closed by applying pneumatic pressure to the open face,267, or the close face, 268, respectively, of the drive piston, 269,while venting the opposite face via the pipes, 270, and, 271. Pneumaticpressure and venting are applied to the pipes, 270, 271, as well as thecorresponding pipes of the other valves or actuators in the group to besimultaneously opened or closed, by the cam driven spool valve, 272,which is moved up by the lifted section, 273, of the cam, 274, and ismoved down by the return spring, 275. As shown in FIG. 16, the spoolvalve, 272, is up on the cam lifted section, 273, and pneumatic pressurefrom pneumatic pressure supply pipe, 276, is applied via pipe, 270, tothe open faces, 267, of the drive pistons, or other actuators such asfor refuel or coke removal, while the close faces are vented via thevent, 277, and the valves, 266, is thus opened. When the cam moves onthe spring, 275, will subsequently force the spool valve follower, 278,back on to the cam base circle, 279, and pneumatic pressure will then beapplied via pipe, 271, to the close faces, 268, of the pistons, 269,while the open faces, 267, will be vented via the vent, 280, and thevalves, 266, will then be closed. Each set of valves and actuators whichare to be simultaneously opened or closed will require its own spoolvalve such as, 272, but all can be driven by the same cam, 274, ifproperly spaced angularly thereabout or, alternatively, each spool valvecan be driven by its own cam. In either case, the spool valves and camsmust be so arranged that one set of valves is closed when the next setof valves in the sequence is opened. Hence, the time interval betweenchanges of connectings, tcc, in minutes equals the arc length, indegrees, of the lifted section, 273, divided by 360 times therevolutions per minute of the cam, 274. A fixed cam speed will yield afixed value of tcc and hence also of tc. But tcc and tc can be adjusted,if desired, by use of an adjustable speed cam drive mechanism such asthe hydraulic drive scheme shown schematically in FIG. 17. An adjustableswash plate hydraulic pump, 281, is driven, as via a reduction gear box,282, from the compressor shaft, 283, and the pump displacement can beadjusted by adjusting the swash plate via the pump control lever, 284.The hydraulic motor, 285, of fixed displacement, drives the spool valvecam, 274, and is itself driven via the pressure line, 286, from thepump, 281, hydraulic fluid return being via the pipes, 287, 288, and thefluid reservoir, 289. The hydraulic motor, 285, speed and hence the camspeed can be adjusted by adjusting the hydraulic pump, 281, displacementvia the lever, 284, increasing pump displacement increasing motor speedand vice versa. Increasing pump displacement increases cam speed andhence shortens the cycle time and vice versa. In this way, the cycletime can be adjusted either by hand adjustment of the swash plate lever,284, or automatically in response to container pressures reached duringcompression. One example automatic cam speed control device is alsoshown in FIG. 17 and comprises a piston, 290, which adjusts the swashplate lever, 284, an adjustable spring, 291, acting in opposition to gaspressure applied to the piston, 290, via the bleed check valve, 296,from the pipe, 292, the opposite piston face being vented to atmospherevia the passage, 293. The pipe, 292, connects to the highest pressurecompressor stage delivery end. The bleed check valve, 296, allows readyflow of compressed gas into the cylinder, 294, but only a slow bleed ofreturn flow out of the cylinder and hence the pressure in the cylinder,294, will be reasonably steady and close to the maximum gas pressureexperienced in the pipe, 292. Thus, as maximum container compressionpressure rises, the piston, 290, moves the swash plate lever, 284, inthe direction, 295, which increases pump displacement to speed up themotor, 285, and cam, 274, and hence to shorten the cycle time. Asmaximum container compression pressure decreases, the lever, 284, ismoved in the direction, 297, which slows the cam, 274, and lengthens thecycle time. In this way, the devices shown in FIG. 17 can function tohold maximum compression pressure at or near a desired value and thisdesired value can be adjusted by adjustment of the spring control nut,298. An adjustable speed electric motor could be substituted for theadjustable speed hydraulic drive.

Wholly mechanical cycle time interval controllers can also be used withthe cams acting directly as valve actuators and refuel or coke removalactuators.

While the cycle time is determined by the rate at which the compressorcan pump up the containers to the maximum cycle pressure, the expandersare required to expand the reacted gases within these containers backdown to minimum cycle pressure within that portion of the cycle timeavailable for expansion. This assurance of adequate expansion can beobtained by use of the expander flow rate controllers already describedhereinabove. So that the time interval between changes of gas flowconnectings, tcc, can be the same for all of the several containers inuse on an oxidation gasifier with a multistage compressor, a multistageexpander, and sealed pressure vessel containers, the ratio of containerpressure rise across a single stage to the mass flow rate of all gasesinto the container connected to that stage shall be equal for allcompressor stages, and further, the ratio of container pressure dropacross a single stage to the mass flow rate of all gases out of thecontainer connected to that stage shall be equal for all expanderstages.

One example of an expander flow rate control scheme is showndiagramatically in FIG. 18 wherein an expander inlet pipe, 299, suppliesreacted gas from connected containers to the adjustable, non-rotatinginlet nozzle guide vanes, 300, which direct the expanding reactant gasesagainst the rotating turbine blades, 301, to produce work. The nozzleflow area between the inlet guide vanes, 300, can be adjusted byrotating these guide vanes about their pivots, 302, by the levers, 303,with each guide vane, 300, having a lever, 303, and these levers areconnected together by links, 304, so that all inlet guide vanes arerotated together similarly. The levers, 303, are thusly rotated by thearm, 305, moved in turn by a nut fitting the threaded shaft, 306. Thethreaded shaft, 306, is rotated so as to open the nozzle flow area bythe open motor, 307, and is rotated so as to close the nozzle flow areaby the close motor, 308, these being electric motors and preferablyconstant speed electric motors. The expander inlet pipe, 299, is fittedwith a high pressure cut in switch, 309, which closes whenever the inletpressure exceeds the value set on this switch, and a low pressure cut inswitch, 310, which closes whenever the inlet pressure is at or below thevalue set on this switch. The set value for the high pressure switch,309, is set, as by hand, to equal or slightly exceed the intendedmaximum expander inlet pressure. The set value for the low pressureswitch, 310, is set, as by hand, to equal or be slightly less than theintended minimum expander inlet pressure. Whenever expander inletpressure exceeds the intended maximum pressure, the open motor, 307, isenergized via the power source, 311, the high pressure switch, 309, andthe open limit switch, 312, and the nozzle flow area is increased inorder to empty the connected containers more quickly so that theintended minimum pressure will be reached during the time periodavailable. The open limit switch, 312, prevents further nozzle openingafter full opening has been reached and the lever, 305, has engaged andopened the limit switch, 312, preventing energizing of the open motor,307. Whenever expander inlet pressure is below the intended minimumpressure, the close motor, 308, is energized via the power source, 31l,the low pressure switch, 310, and the close limit switch, 313, and thenozzle flow area is decreased in order to decrease the rate of emptyingof the next connected container so that the expander inlet pressure willnot drop below the intended minimum pressure during the time periodavailable. The close limit switch, 313, prevents further nozzle closingafter maximum closing has been reached and the lever, 305, has engagedand opened the limit switch, 313, preventing energizing of the closemotor, 308. This expander flow rate control scheme thus acts to assurethat each container is expanded down to essentially the same desiredminimum pressure within the time period available. An electricallyenergized expander flow rate controller is shown in FIG. 18 buthydraulic or pneumatic control schemes can also be used as is well knownin the art of expander flow rate controllers. Nozzle flow area iscontrolled by the scheme shown in FIG. 18 but a similar control couldact instead to adjust a throttle valve in the expander inlet pipe or toadjust the cut-off timing on a piston expander.

Chemical analysis of the complete combustion gases leaving the containerduring expansion can be used as an alternate sensor and control meansfor controlling the ash volume inside the container. As ash volumeincreases at essentially constant quantity of char fuel plus ashes, thechar fuel quantity decreases, thus increasing the amount of oxygen gasunuseable and thus present in the expansion gases leaving the container.As ash volume decreases at essentially constant quantity of char fuelplus ashes, the char fuel quantity increases, thus decreasing the amountof oxygen gas unused until eventually some of the carbon monoxideemerging from the char pores remains unburned and is thus present in theexpansion gases leaving the container. One example of such a chemicalanalysis type ash volume sensor and control scheme is shownschematically in FIG. 12 and comprises, a timed gas sampling valve, 126,and sample nozzle, 127, an automatic exhaust gas analyzer andcontroller, 128, an output to the coke removal interrupter switch, 131,and an operating power input, 129. The sampling valve is opened andclosed by the solenoid and spring actuator, 130, which connects as showninto the solenoid energizing circuit of FIG. 10, with one samplingvalve, 126, and actuator, 130, for each container. When a container, sayB, connects to a selected expander stage, for example the last expanderstage, at BX2 with solenoid power terminal T3 energized, the samplevalve actuator, BS, for that container is also energized opening thesample valve, 126, and delivering a sample of the expansion gases to theexhaust gas analyzer and controller, 128. When the gas analyzer findsexcess oxygen gas in the expansion gas, the controller closes the cokeremoval interrupter, 131, for that container, BCR, so that ashes will beremoved at the next coke removal time interval, thus dropping the charand ash pile height and causing more char fuel to be added into thatcontainer. When the gas analyzer finds excess carbon monoxide in theexpansion gas, the controller opens the coke removal interrupter, 131,for that container, BCR, and coke removal ceases causing ash volume toincrease and thus decreasing the char fuel volume since char burnupcontinues. The levels of excess oxygen gas and excess carbon monoxide atwhich the controller acts thusly upon the coke removal interrupter, 131,can be set by the knobs, 132, 133. The sampling valve, 126, can bethusly opened when each container connects to any one selected expanderstage, such as the last stage as described above, and the best timingfor this sampling valve is preferably determined experimentally.

This ash volume sensor and coke removal control scheme using chemicalanalysis of the complete combustion gases leaving a container duringexpansion can alternatively be adopted for use as a direct char fuelvolume sensor and refuel control scheme by holding a constant ash levelwith a separate ash level sensor and control such as described abovepreviously instead of holding a constant char fuel and ash level as usedfor the above example. For this char fuel volume sensor application, thecontroller will act to close the refuel interrupter, 121, when theoxygen gas content exceeds a set value to cause refueling to occur, andwill act to open the refuel interrupter, 121, when the carbon monoxidecontent exceeds a set value to prevent refueling. This direct char fuelvolume sensor and control scheme may be preferred when ash removaloccurs continuously in a molten state.

Use of the above-described chemical analysis schemes for control of charfuel volume and ash volume inside each container also provides a methodfor minimizing efficiency losses due to excess air or incomplete burningof carbon monoxide. Some excess air will be needed to assure essentiallycomplete burning during secondary reaction of the carbon monoxide andhydrogen emerging from the char pores during expansion. But this excessair quantity needs to be minimized to reduce the resulting exhaustenthalpy losses and particularly to reduce the work losses due tocompression and reexpansion of this excess air quantity. If we reducethe excess air quantity too greatly, losses due to incomplete burning ofcarbon monoxide will result. As char fuel volume, and hence pore volume,increases more air is reacted to carbon monoxide inside the pores andless excess air is available since the dead volume decreases. Thus, amaximum preferred char fuel volume exists above which appreciableunburned carbon monoxide will exist in the expansion gases and losseswill result. As char fuel volume, and hence pore volume, decreases, lessair is reacted to carbon monoxide by the primary reaction inside thepores and more excess air is available since the dead volume increases.Hence, a minimum preferred char fuel volume exists below whichappreciable unneeded excess air is being used and losses will result. Bysensing oxygen gas content and carbon monoxide content of the expansiongases and controlling the refuel and coke removal mechanisms asdescribed above, these chemical analysis schemes can function to holdthe char fuel volume between these preferred maximum and minimum valuesand thus to optimize plant efficiency.

These refuel and coke removal schemes described above are examples andother schemes can alternatively be used.

Where changeable water flow connections are used, as in some forms ofthe invention with radiant heaters in series as in FIG. 5, these andtheir means for opening and closing and their means for controlling themeans for opening and closing can be essentially similar to thechangeable gas flow connections and their means for opening and closingand their means for controlling the means for opening and closing asused on the cyclic oxidation char gasifier portion of the cyclic Veloxboiler and as described in the application Ser. No. 06/328,148. Thechangeable water flow connection scheme can be entirely separate fromthe changeable gas flow connection scheme but the means for controllingis preferably combined since all changes of connections are to occurpreferably at the same time. For example, the means for controlling theopening and closing of changeable gas flow connections shown in FIGS. 10and 11 can be readily modified to also control the opening and closingof changeable water flow connections. This modification comprisesconnecting the means for opening and closing the changeable water flowconnections between the solenoid power source ground and the solenoidpower input terminals T1, T2, T3, T4, T5, T6, so that when these areenergized in sequence via the cascade relay scheme, the changeable waterflow connections are changed in sequence so as to always maintain thedesired water flow direction through the series connected radiantheaters. The preferred water flow direction through series connectedradiant heaters is with the water entering first that radiant heaterwhose container is connected to the first compressor stage outlet withthe water flowing next in series through radiant heaters whosecontainers connect to compressor stages in the direction of increasingcompressor stage delivery pressure. Thereafter, the water flow directionis preferably in series through radiant heaters whose containers connectto expander stages in the direction of increasing expander stage inletpressure. In many cases extra containers are used, in excess of the sumof the number of expander stages plus the number of compressor stages,so that refuel and coke removal can occur at low pressure when acontainer is not connected to either a compressor outlet or an expanderinlet. For these extra container cases, the coldest water is preferablypassed first into those radiant heaters inside containers undergoingrefueling and coke removal and the water flow direction then continuesnext into radiant heaters inside containers connected to compressorstages as described above.

Radiant heaters can also be connected in series with fixed water flowconnections instead of changeable water flow connections and a simplerplant results. An example of such a fixed series connected radiantheaters cyclic Velox boiler plant is shown schematically in FIG. 13 andcomprises: a compressor, 151, with three stages, 152, 153, 154, whoseoutlets, 155, 157, 158, connect via changeable gas flow connections,159, 160, 161, to containers being compressed, 162, 163, 164; a lowpressure expander, 165, with two stages, 166, 167, whose inlets, 169,170, connect via changeable gas flow connections, 172, 173, tocontainers being expanded, 175, 176; a high pressure single stageexpander, 168, whose inlet, 171, connects via the changeable gas flowconnection, 174, to a container first being expanded, 177; a powermeans, 178; a compressor first stage inlet air density settingcompressor and gas turbine drive means, 179; a feedwater pump and drivemeans, 180, with controller, 203; a feedwater heater, 181, on the lowpressure expander exhaust; a convection heater, 189, on the highpressure expander exhaust; three convection heaters, 194, 195, 196, onthe three expander inlets, 169, 170, 171, respectively; an extracontainer, 197, undergoing coke removal, and an extra container, 198,undergoing refueling; an exit boiler steam pressure sensor, 199, and anexit steam temperature sensor, 200; a gas pressure reducing valve, 201,with controller, 202. This cyclic Velox boiler shown in FIG. 13 is anexample of a once-through boiler with the feedwater from a source, 204,being pumped against boiler pressure by the feedwater pump, 180, throughthe several heaters, all fixedly connected in series in the followingdirection: first throough the feedwater heater, 181; then through theradiant heaters inside containers in the direction starting atcontainer, 198, through containers, 197, 162, 163, 164, 175, 176, 177,and always in that order of containers independently of how thesecontainers change their connections to the compressor outlets and refueltransfer means and coke removal transfer means and expander inlets; thenthrough the high pressure expander exhaust convection heater, 189; thenthrough the convection heater, 194, on the lowest pressure expanderinlet, 169; then through the convection heater, 195, on the intermediatepressure expander inlet, 170; last through the convection heater, 196,on the highest pressure expander inlet, 171. The boiler pressure sensor,199, acts via the controller, 202, and gas pressure reducing valve, 201,which admits expansion gases to drive the gas turbine drive of theintake compressor, 179, to increase compressor air intake density whensteam pressure decreases below a set value and to decrease compressorair intake density when steam pressure increases above a set value. Inthis way, the char fuel burn rate is controlled to control boiler steampressure. The boiler steam exit temperature sensor, 200, acts via thefeedwater pump controller, 203, to increase feedwater flow when thesteam temperature exceeds a set value and to decrease feedwater flowwhen the steam temperature drops below a set value. In this way, theexit steam temperature is controlled within set limits. This fixedseries connected once through cyclic Velox boiler of FIG. 13 can be usedat any steam pressure including pressures at or above the criticalpressure of water.

Where the several radiant heaters are in parallel a sensor, to measuresteam enthalpy at each radiant heater steam outlet, acting via a controlmeans to control the distribution of water flow to that radiant heatermay be preferred on each radiant heater especially where water flowthrough radiant heaters is not large as, for example, with once-throughboilers. One example of such a steam enthalpy sensor and flowdistribution controller is shown schematically in FIG. 14 and comprises:a tube wall temperature sensor, 205, mounted in one or more of theradiant heater tubes, 53, on a portion thereof which views the burningchar fuel pile; a controller, 206, responsive to the tube walltemperature sensor, 205, and operative upon the opener and closer means,207, of the flow distributor valve, 208; a flow distributor valve, 208,which adjusts the flow area, 209, through which water enters the radiantheater inlet, 55, and hence the flow rate of water distributed to theradiant heater; a bypass flow passage, 210, which assures that somewater always flows to each radiant heater section inlet, 55. The openerand closer means shown in FIG. 14 comprises a reversible electric motor,211, driving the threaded shaft, 215, of the tapered area adjustor, 212,via a gear box, 213, and a slideable splined coupling, 214, so thatelectric motor rotation in the increase direction increases the flowarea, 209, and hence the water flow quantity entering that radiantheater, and so that electric motor rotation in the decrease directiondecreases the flow area, 209, and hence the water flow quantity enteringthat radiant heater. The electric motor, 211, is energized from thepower source, 216, either in the increase direction via the increaseswitch, 217, and increase limit switch, 218, or in the decreasedirection via the decrease switch, 219, and decrease limit switch, 220.When tube wall temperature sensed at, 205, is above a set value thecontroller, 206, opens the decrease switch, 219, and closes the increaseswitch, 217, to increase water flow area, 209, and water flow and thusacts to decrease tube wall temperature. When tube wall temperaturesensed at, 205, is below a set value the controller, 206, opens theincrease switch, 217, and closes the decrease switch, 219, to decreasewater flow area, 209, and water flow and thus acts to increase tube walltemperature. The limit switches, 218, 220, function to stop the electricmotor, 211, before mechanical interference occurs. Other types of steamenthalpy sensors and flow distribution control means can also be usedfor the purposes of this invention.

The various radiant heaters and convection heaters are pressure vesselson their steam sides requiring adequate wall thickness to withstand fullboiler steam pressure at operating temperatures. The containers, withinwhich radiant heaters may be mounted, are also pressure vessels on theircombustion gas sides and require adequate wall thickness to withstandthe maximum reactant gas pressure applied by the compressor duringcompression. Convection heaters on expander inlets are also pressurevessels on their gas sides and require adequate wall thickness towithstand the maximum pressure applied by containers when connected tothat particular expander inlet. These boiler heaters which are pressurevessels on both the steam side and the gas side are preferably arrangedso that the gas side pressure vessel is integral with or at least incontact with the steam side pressure vessel. With this preferredintegral pressure vessel, additional heat transfer area is provided tothe steam side pressure vessel and cooling is provided to the gas sidepressure vessel. This integral pressure vessel arrangement is shown inFIGS. 3 and 4 wherein the gas side pressure vessel wall, 54, is securedto all of the steam side pressure vessel tube walls, 53, as by welding.Commonly the radiant heater container pressure vessel walls, 54, areinsulated to reduce heat loss on the side opposite the combustionchamber.

The largest fluctuation of net rate of work output occurs at each changeof connectings. Just prior to the change all containers being compressedare near to full pressures for the interval and compressor work rate ismaximum, whereas all containers being expanded are near to minimumpressures for the interval and expander work rate is minimum, the oneexpanding container about to disconnect from the expander producingessentially no work. Just after a change of connectings, all containersbeing compressed are at lowest pressures for the interval, the onecontainer just connected to the lowest pressure stage of the compressorrequiring essentially no work, whereas all containers being expanded areat maximum pressures for the interval and expander work rate is maximum.This largest work rate fluctuation can be approximated as equal to thesum of the maximum work rate of the lowest pressure stage of thecompressor and the maximum work rate of the lowest pressure stage of theexpander and clearly can be made as small as required by increasing thenumber of compressor stages, nc, and by increasing the number ofexpander stages, nx. In FIGS. 1 and 2 the number of compressor stages isshown equal to the number of expander stages but this is not necessary.An expander stage as herein defined may be a work output producingexpander engine or a non work output producing blowdown expander.Additionally, these power output variations can be reduced toessentially zero by use of the devices described in my cross-referencedU.S. patent application entitled, "Torque Leveller," Ser. No.06/403,923, filing date July 30, 1982. For example, the leveller enginecan be a steam turbine using all or some of the steam generated in thecyclic Velox boiler plant.

Several control means are described herein for control of thecompressor, the expander, the feedwater pump, the combustion steam,etc., and these controls are described as operating separately. In manyapplications we may prefer to use an integrated control system whichcould also include the steam turbine and electric generator controls ofa steam power cycle. These various separate control means can becombined into an integrated control system by methods already well knownin the art of control systems such as those described in chapter 35 ofreference D.

As compression proceeds each primary air mass increment enters the charpores and reacts there into primary reacted gas, being thereafterfurther compressed. Hence, each reacted gas increment reacts at adifferent pressure and hence temperature and, being thus at a differentreacted gas temperature, has a different work of compression done uponit when compressed up to the final pressure. This manner of differingcompression plus reaction plus further compression produces severalresults:

(1). The final compressed reacted gas has a large temperature gradientsince each gas mass had a different amount of work of compression doneupon it.

(2) The work of compression upon the primary reacted gas in the poresand the air in the dead volume inside the container is done by the flowwork of those air masses later compressed into the container.

(3) The secondary and excess air mass increments do not react duringcompression and hence these have equal net work of compression and notemperature gradient.

(4) Each incremental air mass, forced by the compressor into thecontainer, divides into two portions, a primary air portion going intothe char pores and a secondary and excess air portion going into thedead volume. These portions change relatively as compression proceedsdue to the different "compressibilities" of those gases already insidethe pores and those gases already inside the dead volume. It is thetemperature gradient of the pore gases and its absence in the deadvolume gases which produces this difference of "compressibility."Initially, the dead volume incremental portion is relatively the largerwhereas subsequently the pore volume incremental portion increasesrelatively.

(5) To produce a given incremental rise in pressure inside thecontainer, a different added mass is required into the pore volume thaninto the dead volume and the ratio of these two masses changes duringcompression. Hence, the schedule of air mass compressed versus pressurerise produced by the air compressor is different when compressing acontainer full of reacting char fuel as against compressing a deadvolume container. This affects the work of the compressor, which is thesum of the incremental products of air mass compressed times enthalpyrise produced at the time and pressure of air mass delivery into thecontainer.

As expansion proceeds, the pressure drop during each time incrementcauses an increment of primary reacted gas to leave the pore volume andto enter the dead volume where it reacts with a secondary air massincrement to produce secondary reacted gases at an even highertemperature. But these secondary reacted gases will preferably all leavethe dead volume during the time increment if the same pressure drop isalso to take place there. Some of the excess air in the dead volume mayalso have to leave during the time increment so that the pressure dropin the dead volume will equal that in the pore volume and this air willbe excess air since it will not be used to react with any of the primaryreacted gases. Again, due to the differing "compressibilities," orrather "expansibilities," of the pore gases from the dead volume gases,for a given pressure drop the mass increment to be removed from the porevolume changes relative to the mass increments to be removed from thedead volume as expansion proceeds. The mass increment from the porevolume is relatively larger at the start of expansion and then, asexpansion proceeds, the mass increment from the dead volume increasesrelatively. Hence, it is preferably during the later and lower pressureparts of the expansion that the excess air leaves the dead volume. Atleast some excess air is thus needed in the dead volume to assure thatsufficient secondary air can be removed from the dead volume as to fullyburn the emerging primary reacted gases during the early part ofexpansion.

The manner in which the secondary reacted gases and excess air actuallyleave the container during expansion depends also on the location of theexit pipe relative to the char fuel mass.

(a) If the exit pipe entry port is located far away from the char fuel,and hence from where the secondary reacted gas is being formed, mostlyair alone will be first to leave the container and secondary reactedgases will leave later. In this case, we are refilling the dead volumewith secondary reacted gases. Here we run the risk of using up all theair in the dead volume, by early outflow and by early reaction, beforeexpansion is complete. The last portions of primary reacted gas to leavethe pores will not then find any secondary air available for theirburning and unburned gas fuel losses will result, or else a largequantity of excess air will be needed producing high compressor-expanderlosses.

(b) If the exit pipe entry port is located too close to the char fuel,some of the primary reacted gas may leave thereby before reacting withsecondary air and thus escape through the expander as an unburned fuelgas loss.

(c) Ideally, the exit pipe is located close enough to the char fuel sothat all of the secondary reacted gases flow first out the exit but notso close that any primary reacted gas can escape unburned.

This ideal exit pipe entry port location may well differ at differingchar burn-up rates. Hence, for some applications we may prefer severalentry ports for the exit pipe and these positioned differently relativeto the char fuel mass. Additionally, dampers can be placed in at leastsome of these several exit pipe entry ports and adjusted so as toproduce the desired relative flow of fully burned secondary reactedgases and excess air. This adjustment of the exit pipe entry portdampers can be done by hand or preferably automatically in response toanalysis of the exit gas content of unburned carbon monoxide gas or thecontent of both unburned carbon monoxide gas and oxygen gas from excessair. With automatic damper control, the dampers can be readily adjustedwhile each container is being expanded from maximum pressure down tofinal pressure. If dampers are placed in all of the exit pipe entryports, at least two of these dampers are preferably to be interconnectedso that net total entry port area is always at least equal to that of asingle entry port in order to avoid undesirable expansion gas throttlinglosses. These exit pipe multiple entry ports with dampers and adjustmentmeans are a means for controlling the relative flow of gases, from thedead volume adjacent to the char fuel mass, and from the dead volumeaway from the char fuel mass, out of each container during expansion, sothat essentially all of the primary reacted gas leaving the pore volumeof the char fuel mass is essentially completely burned with secondaryair, and also so that the required excess air quantity is minimized.

One example of such a means for controlling the relative flow of gasesduring expansion out of a container, 11, is shown schematically in FIG.15, and comprises:

(a) an exit pipe entry port, 221, rather close to the char fuel pile,43, and fitted with a damper valve, 223, with control lever, 225:

(b) another exit pipe entry port, 222, rather far away from the charfuel pile, 43, and fitted with a damper valve, 224, with control lever,226;

(c) a third exit pipe entry port, 227, at an intermediate positionrelative to the char fuel pile, 43, and not fitted with a damper valve;

(d) a gas sample nozzle, 228, located in entry port, 221, directs a gassample to the carbon monoxide analyzer and controller, 229, operativeupon the actuator, 230, which adjusts the damper valve, 223, via itslever, 225;

(e) another gas sample nozzle, 231, located in the final exit pipe, 232,directs a gas sample to the oxygen gas analyzer and controller, 233,operative upon the actuator, 234, which adjusts the damper valve, 224,via its lever, 226.

When carbon monoxide content of the sampled gases exceeds a small setvalue, the controller, 229, acts via the actuator, 230, to move thedamper, 223, so as to reduce the flow area of that entry port, 221,closest to the char fuel pile. When oxygen gas content of the sampledgases exceeds a set value, the controller, 233, acts via the actuator,234, to move the dampers, 224, so as to reduce the flow area of thatport, 222, farther away from the char fuel pile. The set values forcarbon monoxide content and oxygen gas content can be adjusted via theknobs, 234, 236, so as to minimize plant losses due to unburned carbonmonoxide on the one hand or too large an excess air quantity on theother hand. The entry ports, 221, 222, 227, may also be positioned atseveral angular positions around the char fuel pile, 43.

The expansion work done by the gases inside the container is deliveredto the expander engine as a flow work input to the expander. Theexpansion work done by the primary reacted gases while within the charpores will essentially equal the compression work previously done uponthese same gases during compression, provided the primary reaction ofair and carbon occurs promptly when the primary air enters the porevolumes. In this way, each increment of primary reacted gas emerges fromthe char pores at essentially the same pressure at which it was formedwhen the air mass increment from which it was formed entered the charpore volume. As each increment of primary reacted gas thus emerges fromthe char pores, it reacts further and preferably completely with anincrement of secondary air from the dead volume and the resultingsecondary reacted gas mass increment then flows preferably promptly outof the container and into the expander. In addition an increment ofexcess air from the dead volume may also flow concurrently out of thecontainer and into the expander. Hence, two different kinds of gases mayconcurrently leave the container and enter the expander with eachincrement of pressure decrease; a secondary reacted gas mass at veryhigh temperature and an excess air mass at rather low temperature. Theincrement of expander engine work done by each of these expanding gasmass increments equals the product of their enthalpy drop across theexpander, which will be much larger for the high temperature secondaryreacted gas than for the colder excess air, and the separate massincrements. But as already described the relative separate massincrements also vary for different pressure drop increments duringexpansion. Both of these effects, the difference of enthalpy drop andthe difference of relative mass increment, affect the work of theexpander, which is the sum of the incremental mass times enthalpy dropproducts for both of the separate gases at each expansion pressure dropincrement.

E. Plant Sizing

Most commonly a cyclic Velox boiler will be sized to produce a selectedsteam quantity at selected boiler input and output steam conditions.Preferably, measured data from pilot plant experiments are used to sizethe several elements of a cyclic Velox boiler. For example, thefollowing quantities can be measured and calculated from pilot plantexperiments with a carbon fuel:

(mf)=char fuel firing rate, mass per unit time

(ms)=boiler steam generation rate, mass per unit time

(mc)=carbon fuel firing rate, mass per unit time

(ma)=compressor air flow rate, mass per unit time

(mcs)=combustion steam flow rate, mass per unit time

(mx)=(ma)+(mc)+(mcs)=expander gas flow rate, mass per unit time

(hsx)=boiler outlet steam enthalpy, energy units per unit mass

(hsi)=boiler inlet feedwater enthalpy, energy units per unit mass

(LHVF)=char fuel lower heating value, energy units per unit mass

(LHVC)=carbon lower heating value, energy units per unit mass ##EQU3##a=molal combustion steam to oxygen ratio ##EQU4## (exa)=fractionalexcess air ##EQU5## The quantity, (exa), can also be measured viaanalysis of the expander exhaust gas.

(MA)=molecular weight of air

G=pore oxygen gas ratio, oxygen gas into char pores divided by totaloxygen gas compressed into container ##EQU6## RP=pore volume ratio, charpore volume divided by total gas space volume inside container

RP=(VP)/(VR)

(VP)=pore volume of all active containers, volume units ##EQU7## (%Pore)=precent porosity of char fuel (CGV)=char fuel gross volume in allactive containers, volume units

The quantities, exa, G, and RP can be varied during pilot plant tests invarious ways, such as adjusting the height and hence the gross volume,CGV, of the char fuel.

(VR)=gas space volume in all active containers, volume units ##EQU8##(VT)=total internal volume of all active containers, volume units(fD)=dead gas space volume fraction not occupied by char fuel

(fA)=fraction of total volume occupied by ashes

(fD)=(1-RP)

(nc+nx)=number of active containers being compressed or expanded

(nc)=number of compressor stages

(nx)=number of expander stages

(tc)=cycle time for one container to undergo a full cycle of compressionand expansion, time units

(PM)=maximum compression pressure, force per unit area

(PO)=starting compression pressure, force per unit area

(PR)=compression pressure ratio=(PM/PO)

(wca)=actual compressor work input per unit mass of air compressed,energy units per mass unit

(efc)=compressor isentropic efficiency, fractional

(wxa)=actual expander work output per unit mass of air compressed,energy units per mass unit

(efx)=expander isentropic efficiency, fractional

(wna)=net work output per unit mass of air compressed, energy units permass unit

(wna)=(wxa)-(wca)

(efa)=work output efficiency of the compressor expander, fractional##EQU9## (wca)(ma)=compressor power input (wxa)(ma)=expander poweroutput

(wna)(ma)=net power output

(TGMA)=expander maximum inlet gas temperature, absolute degrees

qB=fraction of total heat of combustion of carbon transferred to boilersteam up to the expander inlet

Measurement of the value of qB requires measuring boiler steam enthalpyout of the last heaters up to the expander inlet, hsz, in addition tothe boiler inlet and outlet steam enthalpies. ##EQU10## (Δwna)=change innet actual work output per unit mass of air compressed, from just beforea change of gas flow connectings to just after a change of gas flowconnectings

(EB)=true boiler efficiency, fractional ##EQU11## (MB1)=averagemolecular weight of primary burned gases inside pores(CPB1)(MB1)--specific heat at constant pressure of primary burned gases,energy units per mol of primary gas

These measured and calculated data can be more useful when graphed indimensionless form to permit interpolation between pilot plant datapoints and, to some extent, extrapolation beyond the data. For example,graphs of the following would be useful for plant sizing purposes:

(a) Plot the ratio (G/1-G) against the ratio (RP/1-RP) for thosepreferred values of G and RP at which the least excess air, (exa), wasuseable without appreciable losses due to incomplete combustion. Aseparate graph can be drawn for each different value of the factor, BF:##EQU12## wherein: (QR1)=heat of primary reaction inside pores in energyunits per mole of oxygen gas reacted in primary reaction

k=specific heats ratio

(b) Plot (TGMA) against (qB). A separate graph can be drawn for eachdifferent value of (PR) and on each such graph separate lines can bedrawn for each different value of (a).

(c) Plot (efa) against (PR). A separate graph can be drawn for eachdifferent value of (TGMA). For use in sizing full-scale plants, themeasured values of (efa) are preferably corrected for the usually highervalues of (efc) and (efx) applicable to larger plant sizes.

(d) Plot (Δwna) against (nc+nx).

(e) Plot the ratio, (mc/ms), against (EB). For use in sizing full-scaleplants, the measured values of (EB) are preferably corrected for theusually higher values applicable to larger plants.

(f) Plot the ratio, (ma/mc), against (exa) for those preferred values of(exa) at which only negligible incomplete combustion losses occurred.

(g) Plot (VR/tc) against (ma). A separate graph can be drawn for eachdifferent value of (RP) and on each such graph separate lines can bedrawn for each different value of (PR). The value of (a) also somewhataffects these lines.

From the foregoing measured pilot plant data and graphical results, acyclic Velox boiler plant can be sized to meet any desired boiler steamgeneration capacity and steam condition. Alternatively, the cyclic Veloxboiler plant can be sized to meet other capacity criteria, such as adesired value of net power output, (wna)(ma), from thecompressor-expander unit, using these same data and graphs. For anyparticular desired capacity, several different plant designs can be useddepending upon the values selected for various plant operatingconditions of which the following are important:

(1) Increased values of compression pressure ratio, (PR), yield highervalues of work output efficiency, efa, of the compressor-expander unit,but require stronger containers and higher pressure compressors andexpanders and these are more expensive.

(2) Increased compressor inlet air density, by increase of inletpressure, (PO), and/or by decrease of inlet temperature, (TO), increasesair flow rate, ma, carbon burn rate, mc, steam generation rate, ms, andnet power output, (wna)(ma), of the compressor-expander unit, Usually,these effects will be utilized to control plant capacity by control ofcompressor inlet air density as described hereinabove.

(3) Increased maximum expander gas inlet temperature, (TGMA), increasesnet power output, (wna)(ma), and work efficiency, (efa), of thecompressor expander unit, but requires use of more expensive expandermaterials in the expander engine or shortens the useful life of theexpander.

(4) Changing the value of combustion steam to oxygen ratio, a, at leastmoderately affects all of the plant operating conditions, one of theprincipal effects being an increase of convective heat transfer and adecrease of radiation heat transfer to the boiler as (a) is increased.This heat transfer effect can be utilized for steam superheater andreheater control as described hereinabove.

(5) For any particular plant capacity and operating conditions, aparticular value of the ratio, (VR/tc), is required. But severaldifferent values of (VR) and (tc) can be used for any one value of thisratio. Larger values of container volume, (VT), and hence of gas spacevolume, (VR), may yield higher values of boiler efficiency, (EB), sincea greater radiation heat transfer area results.

(6) Increasing the number of active containers, (nc+nx), by increase ofthe number of compressor and/or expander stages, will decrease thevariation of net power output, (Δwna)(ma), but will increase the plantcost. The radiation heat transfer area and hence the boiler efficiency,(EB), can also be increased by increase of the number of activecontainers.

The refuel and coke removal mechanisms are sized to deliver at least themaximum carbon fuel flow rate, mc, and to remove the corresponding ashflow rate. The following relations can be utilized for this sizing ofthe refuel and coke removal mechanisms: ##EQU13## (tf)=refuel timeinterval between refuelings of all active containers, time units

(VF)=refuel volume of each refuel mechanism, volume units

(dch)=char fuel density, mass per unit volume

(% carb.)=percent carbon content of char fuel

Z=refuel ratio, any integer equal to or greater than 1.0

(mr)=mass flow rate of ashes per unit time ##EQU14## (tfr)=coke removaltime interval between removals of ashes from all active containers, timeunits

(VC)=removal volume of each coke removal mechanism, volume units

(dchr)=ash density, mass per unit volume

(% ash)=percent ash content of char fuel

y=coke removal ratio, any integer equal to or greater than 1.0

Any consistent system of units can be used for the various measured andcalculated quantities described above.

The foregoing pilot plant data method for sizing a cyclic Velox boilerplant is preferred. For those cases where pilot plant data areinadequate or unavailable, the following additional analytical equationscan be used for approximate plant sizing calculations: ##EQU15##(TM)=average gas temperature in dead volume at end of compression(TP)=average primary burned gas temperature inside pores at end ofcompression ##EQU16## (PB)=high reference pressure, equivalent to 34atmospheres (PA)=low reference pressure, equivalent to one atmosphere

(FD)=dead gas compression factor ##EQU17## (RAS)=perfect gas constantfor mixture of combustion steam and air

(MAS)=average molecular weight of the mixture of combustion steam andair

(wci)=isentropic compressor work input per unit mass of air compressed,energy units per mass unit

(wxi)=isentropic expander work output per unit mass of air compressed,energy units per mass unit ##EQU18## (MB2)=average molecular weight ofsecondary reacted gases (MB2)(CPB2)=specific heat at constant pressureof secondary reacted gases per mol of gas

(rb2)=9.52+5.76a+(1+a)(a)+(2+a)(exa)(4.76+a) ##EQU19## ΔTRB=total gastemperature rise of secondary reacted gases due to both primary reactionand secondary reaction ##EQU20## (2+a)(QRC)=heat of reaction of carbonburning to carbon dioxide, energy units per mol of oxygen gas reacted

(wca)=(wci)/(efc)

(wxa)=(efx)(wci)

(wna)=(wxa)=(wca)

(efa)=(wna)/(qin) ##EQU21##

The variation of work output, (Δwna), occurring when the changeable gasflow connections are changed can be estimated as follows:

(a) calculate (wca max) and (wxa max) at the true maximum pressure ofcompression;

(b) calculate (wcamin) at the maximum pressure reached by the next tolast container being compressed;

(c) calculate (wxamin) at the starting pressure of the second containerbeing expanded;

(d) calculate estimated (Δwna);

Δwna=(wxamax-wxamin)-(wcamin-wcamax)

The least amount of excess air, examin, to always assure at leaststoichiometric flow of secondary air from the dead volume relative topore gas flow from the pore volume during expansion can be estimated asfollows: ##EQU22##

Select value of (qB) to yield desired value of (TGMA).

Again, any consistent system of units can be used for these additionalanalytical sizing equations.

These analytical sizing equations suffer the errors inherent in theassumptions and approximations made for their derivation of which thefollow are the more important:

(1) all processes assumed isentropic except the primary and secondarychemical reactions;

(2) gases behave as perfect gases with constant specific heats;

(3) heat of reaction constant;

(4) combustion steam and air are not stratified;

(5) primary and secondary reactions occur essentially instantaneouslyupon contact of reactants;

(6) secondary reaction products flow promptly out of containers afterreaction;

(7) primary and secondary reactions go to completion.

These assumptions will tend to cause the calculated work output andefficiency of the compressor-expander unit to be too high.

Various examples of cyclic Velox boiler plants and elements thereof havebeen described hereinabove for purposes of illustration, but it is notintended thereby to limit the invention to these illustrative examples.

Having thus described my invention, what I claim is:
 1. The combinationof a cyclic oxidation char gasifier plant comprising:at least onecompressor means for compressing gases from a lower pressure to a higherpressure and each such compressor means comprising at least one stageand each such stage comprising an inlet and an outlet end; at least oneexpander means for expanding gas from a higher pressure to a lowerpressure and each such expander means comprising at least one stage andeach such stage comprising an inlet end and a discharge end; at leasttwo separate containers, each of said containers comprising pressurevessel means for containing char fuel and any gas compressed into saidchar fuel, each such container comprising interior surfaces on thecombustion side; power means for driving said compressors and forabsorbing any mechanical work done upon said expanders by said expandinggas; each such expander means comprising an expander discharge; at leastone char fuel heater, said char fuel heater comprising means for heatinga portion of the char fuel within each of said containing means to thattemperature at which said char will react rapidly with oxygen inadjacent compressed reactant gases when said cyclic char gasifier plantis being started; at least one reactant gas supply source of gascontaining appreciable oxygen gas; each such compressor whose number ofstages exceeds one further comprising fixed open gas flow connectionsfrom the outlet end of each compressor stage, except one, to the inletend of one other stage of said compressor, whereby said stages of saidcompressor are connected in series so that the pressure of a particulargas means, at delivery from each stage, increases as said gas mass iscompressed through said series connected stages, from the inlet end tothe outlet end of each stage, with the first stage in said seriesthrough which a gas mass first flows being both the lowest pressurestage and also that one stage whose inlet end does not have a fixed opengas flow connection from the outlet end of any other stage of saidcompressor, and with the last stage in said series through which a gasmass last flows being both the highest pressure stage and also that onestage whose outlet end does not have a fixed open gas flow connection tothe supply end of any other stage of said compressor; fixed open gasflow connections from the inlet end of the lowest pressure stage of eachof said compressors to at least one reactant gas supply source of gascontaining appreciable oxygen gas; each such expander whose number ofstages exceeds one further comprising fixed open gas flow connectionsfrom the discharge end of each expander stage, except one, to the inletend of one other stage of said expander, whereby said stages of saidexpander are connected in series so that the pressure of a particulargas mass, at discharge from each stage, decreases as said gas mass isexpanded through said series connected stages, from the inlet end to thedischarge end of each stage, with the first stage in said series throughwhich a gas mass first flows being both the highest pressure stage andalso that one stage whose inlet end does not have a fixed open gas flowconnection from the discharge end of any other stage of said expander,and with the last stage in said series through which a gas mass lastflows being both the lowest pressure stage and also that one stage whosedischarge end does not have a fixed open gas flow connection to theinlet end of any other stage of said expander; fixed open gas flowconnections from the discharge end of the lowest pressure stage of eachof said expanders to said expander discharge; changeable gas flowconnections, which are openable and closeable, from each of saidcontainers to each outlet end of each stage of each of said compressorsand to each inlet end of each stage of each of said expanders; eachcyclic char gasifier plant comprising a number of said containers, withchangeable gas flow connections to said compressors and to saidexpanders, at least equal to the sum of the number of comressor stagesof all compressors, and the number of expander stages of all expanders;at least one refuel mechanism, said refuel mechanism comprising;meansfor transferring a volume of solid materials from a supply source intosaid containing means when said refuel transfer means is connected tosaid containing means; means for connecting said refuel transfer meansto said containing means for a time period for refueling and fordisconnecting said refuel transfer means from said containing means atthe end of said refuel time period; means for sealing said refuel meansfor connecting and disconnecting against gas leakage; at least one cokeremoval mechanism, said coke removal mechanism comprising;means fortransferring a volume of non-gas materials out of said containing means;means for opening and closing said changeable gas flow connections sothat each container is opened for a time period to each outlet end ofeach stage of each of said compressors, in a sub-sequence of timeperiods of open gas flow connections to compressors, said sub-sequenceproceeding in time order of increasing compressor stage deliverypressure, and is opened for a time period to each inlet end of eachstage of each of said expanders, in a sub-sequence of time periods ofopen gas flow connections to expanders, said sub-sequence proceeding intime order of decreasing expander stage inlet pressure, saidsub-sequence of connections to said compressors being followed by saidsub-sequence of connections to said expanders, and these togethercomprise one sequence of time periods of open gas flow connections, eachof said containers is opened to only one stage during any one timeperiod of said sequence of time periods, said sequence of time periodsof open gas flow connections to said compressors and to said expandersis repeated for each of said containers by said means for opening andclosing; means for controlling said means for opening and closing, andsaid means for connecting said refuel transfer means and said cokeremoval transfer means, so that said repeated sequences of time periodsof open gas flow connections, and any time periods available only forrefueling and for coke removal, are a continuous series of time periodsfor any one containing means, and so that the delivery end of each stageof each compressor has an open gas flow connection to one containingmeans, and the inlet end of each stage of each expander has an open gasflow connection to one containing means, during all time periods,whenever said plant is operating; wherein the improvement comprisesadding thereto: boiler means for heating and boiling liquid water atpressure and for heating steam at pressure, and comprising a boilerfeedwater inlet and a boiler steam outlet, at least one portion of saidboiler means comprising at least one radiant heater means positioned onthe interior surfaces of one of said containers, each such radiantheater comprising a liquid water inlet and a water outlet; a source ofboiler feedwater; feedwater pumping means for pumping liquid water intosaid boiler means from said feedwater supply source and comprising adrive means for driving said feedwater pump and a control means forcontrolling the flow rate of water pumped; feedwater pump connectingmeans for connecting said feedwater pumping means to said boiler meansand to said feedwater supply source so that liquid water is forced intosaid boiler liquid water inlet whenever said plant is operating; sensorand control means for sensing the quantity of char fuel within each saidcontainer when said plant is operating and operative upon said means forconnecting said refuel transfer means so that, when the volume of charfuel within any one container becomes less than a minimum set value,said refuel transfer means is connected to that container by said meansfor connecting said refuel means, and when the volume of char fuelwithin any one said container exceeds a maximum set value, said refueltransfer means is disconnected from that container by said means forconnecting said refuel means; whereby said cyclic oxidation chargasifier plant becomes a cyclic Velox boiler plant.
 2. The combinationof a cyclic Velox boiler plant as described in claim 1, wherein:saidboiler means comprises at least two of said radiant heater means; andfurther comprising: series connecting means for connecting said severalboiler radiant heater means in series so that all of the water whichflows through any one of said radiant heater means also flows throughall of said radiant heater means whenever said series connecting meansremains unchanged.
 3. The combination of a cyclic Velox boiler plant asdescribed in claim 1, wherein:said boiler means comprises at least twoof said radiant heater means; and further comprising: changeable waterflow connecting means for connecting the liquid water inlet of each saidradiant heater means to said boiler feedwater inlet, and the wateroutlet of each said radiant heater means to said boiler steam outlet,and said radiant heater liquid water inlets to said radiant heater wateroutlets of different said radiant heater means; means for opening andclosing said changeable water flow connecting means; and further whereinsaid means for controlling said means for opening and closing saidchangeable gas flow connecting means additionally controls said meansfor opening and closing said changeable water flow connecting means sothat water flows through said several radiant heater means in series,and so that during any one time period the water flow direction is inorder, through those radiant heaters inside containers connected tocompressor stages and in the direction of increasing compressor stagedelivery pressure, and then through those radiant heaters insidecontainers connected to expander stages and in the direction ofincreasing expander stage inlet pressure.
 4. The combination of a cyclicVelox boiler plant as described in claim 1, wherein:said boiler meanscomprises at least two of said radiant heater means; and furthercomprising: parallel connecting means for connecting said several boilerradiant heater means in parallel so that said several radiant heatermeans have a common liquid water inlet and a common water outlet; flowdistribution means for distributing water flow to said several radiantheater means so that, said water flow is distributed between saidseveral parallel connected boiler radiant heater means with at leastsome water being always distributed to each said radiant heater means,said flow distribution means connecting between said common liquid waterinlet and the separate liquid water inlets of each said radiant heater.5. The combination of a cyclic Velox boiler plant as described in claim4 and further comprising:steam enthalpy sensor means for separatelysensing the enthalpy of water leaving each of said several radiantheater means; control means responsive to said several separate steamenthalpy sensor means and operative upon said flow distribution meansfor distributing water flow so that said water flow is distributed toeach radiant heater means so that the water leaving any one of saidradiant heater means has approximately the same enthalpy as the waterleaving any other one of said radiant heater means.
 6. The combinationof a cyclic Velox boiler plant as described in claim 1, 2, 3, 4, or 5and further comprising:at least one convection heating means for heatingwater at pressure by means of the combustion gases flowing into theinlet of one of said expander stages and comprising a convection heaterwater inlet, a convection heater water outlet, a steam side, and a gasside; convection heater steam side connecting means for connecting saidconvection heating means into said boiler means so that at least some ofthe water which flows through said radiant heater means flows throughthe steam side of at least one of said convection heater means;convection heater gas side connecting means for connecting each of saidconvection heating means into the inlet of one stage of one of saidexpanders so that all of the combustion gases which flow from connectedcontainers into the inlet of that stage of that expander flow previouslythrough the gas side of that connected convection heating means.
 7. Thecombination of a cyclic Velox boiler plant as described in claim 1, 2,3, 4, or 5, and further comprising:at least one expander exhaust gasmeans for heating water at pressure by means of the combustion gasesflowing through the discharge of at least one of said expanders andcomprising an exhaust heater means water inlet, an exhaust heater meanswater outlet, a steam side and a gas side; exhaust gas heater steam sideconnecting means for connecting each said exhaust gas heater into saidboiler means so that at least some of the water which flows through saidradiant heater means also flows through the steam side of each saidexhaust gas heater means; exhaust gas heater gas side connecting meansfor connecting each said exhaust gas heater into the discharge of atleast one of said expanders so that all of the combustion gases whichflow through said connected expanders flow subsequently through the gasside of each said exhaust gas heater means.
 8. The combination of acyclic Velox boiler plant as described in claim 1, 2, 3, 4, or 5 andfurther comprising:at least one convection heating means for heatingwater at pressure by means of the combustion gases flowing into theinlet of one of said expander stages and comprising a convection heaterwater inlet, a convection heater water outlet, a steam side and a gasside; convection heater steam side connecting means for connecting saidconvection heating means into said boiler means so that at least some ofthe water which flows through said radiant heater means also flowsthrough the steam side of at least one of said convection heater means;convection heater gas side connecting means for connecting each of saidconvection heating means into the inlet of one stage of one of saidexpanders so that all of the combustion gases which flow from connectedcontainers into the inlet of that stage of that expander flow previouslythrough the gas side of that connected convection heating means; atleast one expander exhaust gas means for heating water at pressure bymeans of the combustion gases flowing through the discharge of at leastone of said expanders and comprising an exhaust heater means waterinlet, an exhaust heater means water outlet, a steam side and a gasside; exhaust gas heater steam side connecting means for connecting eachsaid exhaust gas heater into said boiler means so that at least some ofthe water which flows through said radiant heater means also flowsthrough the steam side of each said exhaust gas heater means; exhaustgas heater gas side connecting means for connecting each said exhaustgas heater into the discharge of at least one of said expanders so thatall of the combustion gases which flow through said connected expandersflow subsequently through the gas side of each said exhaust gas heatermeans.
 9. The combination of a cyclic Velox boiler plant as described inclaim 1, 2, 3, 4, or 5, and further comprising:means for setting thedensity of the gas at inlet to said first stage of said compressor meansand comprising a gas inlet and a gas outlet; means for connecting saidgas density setting means outlet to said first compressor stage inletand said air density setting means inlet to said source of gascontaining appreciable oxygen gas; boiler pressure control means forcontrolling boiler steam pressure by controlling the gas density atfirst compressor stage inlet and comprising, a boiler steam pressuresensor and control means operative upon said means for setting thedensity of gas at first compressor stage inlet so that when boiler steampressure decreases below a set value, said gas density increases andwhen boiler steam pressure increases above a set value, said gas densitydecreases.
 10. The combination of a cyclic Velox boiler as described inclaim 1, 2, 3, 4, or 5, and further comprising:a source of steam forcombustion steam; means for delivering steam from said source ofcombustion steam into at least one container while said containers areconnected to compressor stages outlets; means for setting the flow rateof combustion steam into said containers during compression so that theratio of combustion steam flow rate to gas flow rate into each containeressentially equals a set value at each container pressure; at least oneconvection superheater means for heating steam at pressure by means ofthe combustion gases flowing into the inlet of one of said expanderstages and comprising a superheater steam inlet, a superheated steamoutlet, a steam side and a gas side; superheater steam side connectingmeans for connecting said superheater means to said boiler means so thatsaid boiler steam outlet connects to said superheater steam inlet;superheater gas side connecting means for connecting each saidsuperheater means into the inlet of one stage of said expander so thatall of the combustion gases which flow from connected containers intothe inlet of that stage of said expander flow previously through the gasside of said superheater means; superheat control means for controllingthe steam temperature at superheated steam outlet by controlling the setvalues of the ratio of combustion steam to gas compressed into saidcontainers so that, when superheated steam temperature decreases below aset value, said set values of the ratio of combustion steam to gasincrease, and when superheated steam temperature increases above a setvalue, said set values of the ratio of combustion steam to gas decrease,said superheat control means comprising a temperature sensor means forsensing steam temperature at said superheated steam outlet and controlmeans operative upon said combustion steam flow rate setting means. 11.The combination of a cyclic Velox boiler as described in claim 8 whereinthe number of said radiant heater means equals the number of saidcontainers and further comprising:means for setting the density of thegas at inlet to said first stage of said compressor means and comprisinga gas inlet and a gas outlet; means for connecting said air densitysetting means outlet to said first compressor stage inlet and said airdensity setting means inlet to said source of gas containing appreciableoxygen gas; boiler pressure control means for controlling boiler steampressure by controlling the gas density at first compressor stage inletand comprising, a boiler steam pressure sensor and control meansoperative upon said means for setting the density of gas at firstcompressor stage inlet so that when boiler steam pressure decreasesbelow a set value, said gas density increases and when boiler steampressure increases above a set value, said gas density decreases; asource of steam for combustion steam; means for delivering steam fromsaid source of combustion steam into at least one container while saidcontainers are connected to compressor stages outlets; means for settingthe flow rate of combustion steam into said containers duringcompression so that the ratio of combustion steam flow rate to gas flowrate into each container essentially equals a set value at eachcontainer pressure; at least one convection superheater means forheating steam at pressure by means of the combustion gases flowing intothe inlet of one of said expander stages and comprising a superheatersteam inlet, a superheated steam outlet, a steam side and a gas side;superheater steam side connecting means for connecting said superheatermeans to said boiler means so that said boiler steam outlet connects tosaid superheater steam inlet; superheater gas side connecting means forconnecting each said superheater means into the inlet of one stage ofsaid expander so that all of the combustion gases which flow fromconnected containers into the inlet of that stage of said expander flowpreviously through the gas side of said superheater means; superheatcontrol means for controlling the steam temperature at superheated steamoutlet by controlling the set values of the ratio of combustion steam togas compressed into said containers so that, when superheated steamtemperature decreases below a set value, said set values of the ratio ofcombustion steam to gas increase, and when superheated steam temperatureincreases above a set value, said set values of the ratio of combustionsteam to gas decrease, said superheat control means comprising atemperature sensor means for sensing steam temperature at saidsuperheated steam outlet and control means operative upon saidcombustion steam flow rate setting means.
 12. The combination of acyclic Velox boiler plant is described in claim 1, 2, 3, 4, or 5,wherein said coke removal transfer means transfers a volume of non-gasmaterials out of said containing means only when connected to saidcontainer, and further comprising:means for connecting said coke removaltransfer means to said containing means for a time period for cokeremoval and for disconnecting said coke removal transfer means from saidcontaining means at the end of said coke removal time period; means forsealing said coke removal transfer means for connecting anddisconnecting against gas leakage; sensor and control means for sensingthe quantity of ashes within each said container when said plant isoperating and operative upon said means for connecting said coke removaltransfer means so that, when the volume of ashes within any one saidcontainer exceeds a maximum set value, said coke removal transfer meansis connected to that container by said means for connecting said cokeremoval transfer means, and when the volume of ashes within any one saidcontainer becomes less than a minimum set value, said coke removaltransfer means is disconnected from that container by said means forconnecting said coke removal transfer means.
 13. The combination of acyclic Velox boiler plant as described in claim 1 wherein:said boilermeans comprises at least two of said radiant heater means; said boilermeans comprises a steam and liquid water separator means with an inlet,a steam outlet and a liquid water outlet; said boiler means comprises arecirculator means with an inlet and an outlet; and further comprising:parallel connecting means for connecting said several boiler radiantheater means in parallel so that said several radiant heater means havea common liquid water inlet and a common water outlet; flow distributionmeans for distributing water flow to said several radiant heater meansso that said water flow is distributed essentially equally between saidseveral parallel connected boiler radiant heater means, said flowdistribution means connecting between said common liquid water inlet andthe separate liquid water inlets of each said radiant heater; andfurther wherein said boiler means comprises connecting means forconnecting said common water outlet of said radiant heaters to the inletof said steam separator and the liquid water outlet of said steamseparator to the inlet of said recirculator means and the steam outletof said steam separator to the boiler means water outlet; and furtherwherein said boiler means further comprises recirculator connectingmeans for connecting said recirculator means outlet to said boiler meansso that the liquid water recirculated by said recirculator means flowsthrough said several parallel connected radiant heaters.
 14. Thecombination of a cyclic Velox boiler plant as described in claim 1, 2,3, 4, or 5, and further comprising:means for controlling the relativeflow of gases, from a dead volume adjacent to the char fuel mass, andfrom the dead volume away from the char fuel mass, out of each containerduring expansion, so that the quantity of unburned carbon monoxide gasis minimized, and so that the quantity of unreacted oxygen gas isminimized.